Help — how everything works

Carpy puts real box design within everyone's reach — no CAD, no drawing, just decisions. Enter your size and shape a complete finger-joint box: three lid styles plus an open-tray mode, compartment dividers, mixed materials, kerf-perfect joints, and cut-ready files for laser cutters and CNC routers alike. This page walks through every feature. Everything updates live: change a setting, and both the cut layout and the 3D preview redraw instantly.

1 · Getting started

Type your box's Width, Height and Depth, pick a lid style, choose your material thickness — done. The right side of the screen shows the result two ways: the 2D cut layout (exactly what your machine will cut) and the 3D preview (the assembled box). When it looks right, press ⬇ Download SVG.

2 · Dimensions

Sizes can be anything from 20 mm up, as large as your machine can cut. The mm / in switch at the top of the Dimensions card chooses the unit you type in: in inches you can enter decimals (7.875) or fractions (7 7/8), and every measurement in the app — thickness, dividers, kerf, part spacing — follows the switch. Whatever you pick, the cut file is always exported in true millimetres, so it lands at exact size in your cutting software. The Outer / Inner toggle chooses what your numbers mean: Outer is the box's outside footprint; Inner means "I need this much space inside" and Carpy adds the walls for you. The small line beside the toggle always shows the resulting inside space.

3 · The preview — 3D, 2D, explode

Carpy opens in 3D: your box assembled on screen, updating as you type. Drag to rotate, scroll to zoom, right-drag (or Space+drag) to pan. Two sliders sit in the corner: Explode pulls the parts apart so you can inspect every joint, and Open lid (drawer and hinged lids) animates the lid — see how it works and looks before you cut. All clearances are calculated for you.

With dividers in the box, every compartment shows its inside size (width × depth in mm) floating over it — switch the Compartment sizes toggle off for a clean view. You can also drag dividers here, and double-click any segment to remove it; see Dividers.

The 2D button shows the flat cut layout — every part exactly as it will be cut, arranged as an unfolded box so you can see how everything relates. Scroll to zoom, drag to pan, and the ⟳ button re-centres. This is what you download.

Default shows every part in a clean neutral grey — shape and joints stay the focus. Material colours paints them by the actual stock they'll be cut from (it activates once you've picked a material from your library).

4 · Dividers, exact sizes & removing segments ★ partly Premium

Add as many vertical (left–right) and horizontal (front–back) dividers as your box can hold — free for everyone; the only limit is the clearance every divider keeps for strength. They interlock with proper cross-lap joints, tab into the walls and the bottom, and the Height slider controls how tall they stand (the maximum follows your lid style automatically). If you ask for more dividers than the box can safely hold, Carpy caps the count and tells you why.

Under the counts, the sidebar lists every compartment's inside size in millimetres — wall to divider, divider to divider — in the order you see them facing the box (V1 is the left-most vertical divider, H1 the front-most horizontal one). The same sizes float over the compartments in the 3D view.

With ★ Premium those sizes are boxes you can type into: enter 40 for a compartment and its divider moves to make it exactly 40 mm inside; the last compartment takes what is left. Or simply drag a divider in the 3D view — hold it and slide it along its axis; the sizes update as you go. Every segment — the part of a divider between two crossings — moves on its own, so a long compartment can sit beside a row of small ones; where two neighbouring segments end up apart, each becomes its own piece with a half-lap tongue at the crossing, and the crossing divider gets a notch for both. Shift-click segments to pick several (they turn lime) and drag any one of them to move the whole group; Alt-click picks a whole divider at once. Typing a size in the sidebar lines that divider up again. A divider only moves through the free space between its neighbours (or the walls) and always stops one stock thickness short of touching them, so you can never type an impossible layout. Even spacing resets them all to equal compartments, measured on the box's inside.

Removing a segment ★ Premium is how you make room for one longer item without losing the rest of the grid. In the 3D view, point at any divider: the part between two crossings (or between a crossing and the wall) lights up red — double-click it and it is gone. The pieces that remain still tab into the walls and the bottom, and where a piece now ends at a crossing it keeps a short half-lap tongue, so it locks into the divider it meets exactly like a full cross-lap. Compartments that join up show one combined size. Removed segments stay as faint ghosts — click a ghost, or the ✕ next to it in the sidebar, to put it back.

5 · Materials & your library

The primary material is what the box is cut from — type its thickness, or better, pick from your material library. The library stores your real stocks: name, thickness, a display colour of your choice, and a Transparent flag for acrylic and similar. It's free for everyone and remembered between visits. Recognisable names get sensible colours automatically — MDF dark brown, pine cream, acrylic white and see-through — and you can change any of them, any time.

Mixing materials ★ Premium: the + Add secondary material button lets one box cut from up to four stocks — a clear acrylic drawer lid on a plywood box, thin dividers in 3 mm while the shell is 6 mm. Assign each part group (lid, rails, dividers) to any material; every joint automatically adapts to the two thicknesses it connects. Each material card also carries its own Dog bones tick with its own drill bit and bone style (see §6), and every material gets its own finger-size slider in the Joints panel (§8) — so a laser-cut 3 mm MDF lid and a router-cut 12 mm plywood shell coexist in one cut file, each with the right joinery.

With Material colours on, the 3D preview shows your actual stocks — transparent materials render see-through:

6 · Dog bones for CNC ★ Premium

A router bit is round, so it can't cut a sharp inside corner — square fingers won't seat into round-milled slots. Dog bones adds small round reliefs at every inside corner so parts seat fully. It's now set per material: tick Dog bones on any material's card and choose that material's drill bit (presets or custom) and bone style — classic dog-bone, or T-bone horizontal / vertical when you'd rather hide the reliefs in one face of the joint.

Because each material decides for itself, mixed jobs come out right by default: leave bones off on the stock you laser-cut (lasers cut sharp corners and need none) and on for the stock you rout. One firm rule keeps files cuttable: a material must be at least 1 mm thicker than its bit — 3 mm MDF can't take a 3.175 mm bit, and Carpy pauses bones for that material and tells you, rather than producing a broken file. In narrow slots where two reliefs would collide, they merge into a single clean end bore automatically, and corners that a relief would weaken are skipped.

7 · Lid styles

No lid — an open tray. The classic parts bin. Tick Drawer handle ★ Premium and a rounded scoop is cut into the front edge — width, depth and corner rounding each on a slider — turning the open box into a finished drawer for your own furniture and cabinets.

Closed lid — a lift-off cap that sits over the box like a gift box. The cap's corner joints use full-size fingers, the same joinery as the box corners, so the lid is as strong as the body. The Lid height slider ★ Premium deepens the cap skirt; the engineered automatic depth is free.

Drawer lid — the lid slides in a channel between 2 rails on each side, with an optional finger pull hole ★ Premium (size adjustable) and a Corner rounding slider ★ Premium — 0 keeps square corners; up to 15 mm rounds the lid corners, rail ends and wall fronts for a softer look. Use the Open lid slider in 3D to watch it slide.

Hinged lid — a cap that swings open on a built-in hinge cut from your own stock: a round disc bearing and a square locking pin, no metal hardware needed. The walls get small engineered reliefs so the lid swings freely without binding. The Hinge size slider ★ Premium (10–30 mm) scales the disc and its pin — bigger is easier to assemble — and the lid skirts, wall reliefs and divider heights re-engineer themselves around whatever size you pick. The standard 14 mm hinge is free. The Lid height slider ★ Premium works here too: deepen the lid as you like — it never goes below the depth the swing needs.

8 · Joints & kerf

Finger joints are sized automatically from each material's thickness — the badges show the values chosen. Every material in your project gets its own finger size slider right in the Joints panel: on AUTO it tracks that stock's thickness; drag it to override, and the ↺ auto chip brings the automatic value back. The corner offset takes care of itself — every corner starts with a full finger.

Kerf compensation makes joints fit properly: enter roughly what your laser burns away (typically 0.1–0.2 mm) and every finger and slot is offset so parts seat cleanly instead of rattling. Cutting on a CNC router? Leave kerf at 0 — your CAM software's tool offset already handles it.

Find your laser's kerf — a two-minute test

Every laser burns away a slightly different width — it changes with the machine, the lens, the material and even the cutting speed. Guessing gives you loose, rattling joints; measuring gives you joints that seat cleanly with a thin line of glue. The test:

1. In your laser software, draw a plain 40×40 mm square and cut it from the same sheet you'll build the box from, with the same power and speed settings.
2. Measure the cut-out square with calipers, in a few places, and average. It will measure smaller than 40 — the beam ate half the kerf on each side.
3. Kerf = 40 − your measurement. A square that measures 39.85 mm means a kerf of 0.15 mm.
4. Enter that number in Carpy's kerf field and export — your fingers and slots are now offset to seat cleanly at their true size.

Re-run the test when you change material, thickness or lens. If joints come out so tight you need a mallet, lower the value by 0.05; if they are visibly loose, raise it by 0.05. One test square per new material batch is a habit that pays for itself on every box after.

9 · Auto nesting ★ Premium

Turn on Auto nesting and every part is packed onto your raw sheet with minimal waste — set your sheet size per material and the spacing between parts. Multiple materials nest onto separate sheets, and the export delivers them as separate files in one ZIP. Fewer sheets, less offcut, real money saved on every job.

10 · Downloading your cut file

⬇ Download SVG saves your cut file in true millimetres — it imports at exact size into LightBurn, xTool Creative Space, Glowforge, or your CNC CAM software. Before saving, Carpy asks whether to include the part labels in the file: keep them for orientation, or download pure cut paths only. With nesting on, multi-sheet jobs come as one ZIP with a file per sheet.

11 · Save & undo

Carpy remembers your work. Every change is saved in your own browser as you go — close the tab, come back tomorrow, and your last box is still there, with your unit and material choices. Nothing is uploaded; the design lives on your computer, so a different browser or device starts fresh.

↶ Undo and ↷ Redo step back and forward through your changes, or use ⌘Z / Ctrl+Z and ⇧⌘Z / Ctrl+Y. The history is per visit — it clears when you leave the page.

12 · Assembling your box

Test-fit everything once before any glue: Carpy's joints are cut to slide together cleanly, and it is the glue that holds the box — don't expect the parts to stay together by friction alone. Then assemble in this order:

1. Dividers first. Slide the vertical and horizontal dividers into each other at their cross-lap joints until you have the complete grid.
2. Grid onto the base. Set the divider grid onto the bottom panel — the tabs along each divider's lower edge drop into the bottom's slots.
3. Walls around it. Add the four walls: each wall captures the divider ends in its slots and interlocks with the bottom and with its neighbouring walls at the corners. Work around the box, closing the last corner with the whole assembly square.
4. The lid. Drawer lid: fit the rails into the side walls as you close the box (their end tabs lock into the front and back walls), then slide the lid into its channel last. Closed lid: assemble the cap on its own — the four skirts onto the cap top — and set it over the box. Hinged lid: assemble the cap first, place it on the box in its closed position, then push the hinge discs through the skirts into the walls and glue the pins in place while the lid sits where it belongs — that way the pivot lines up exactly and the lid swings freely.

13 · Free & Premium

The free tier is the full generator: any size, every lid style, dividers with every compartment size shown, kerf, your material library, 3D preview and SVG export — no signup needed. Carpy Premium adds the workshop power tools: exact divider placement in millimetres and removing individual divider segments, mixing up to four materials in one box, dog-bone and T-bone reliefs with per-material bits, auto nesting, and the lid fine-tuning set — lid height, hinge size, drawer handle, corner rounding and the finger pull hole. It comes with a 7-day free trial; the current price is always shown in the app. Cancel any time, in two clicks, from Manage subscription.