While you draw, the cursor is pulled onto real geometry — the end of a wall, a solved corner, where two walls cross, the middle of a wall — and only falls back to the grid when none of those is near. G turns grid snapping on and off (the bottom right of the window reads snap on (G)), and Shift locks the direction to the nearest 45°.
What it snaps to, in order
Every candidate near the cursor is collected and the best one wins — first by what kind of point it is, then by how close it is on screen. The order:
| Snap | Catches within | Marker |
|---|---|---|
| Endpoint — the end of a wall | 10 px | square |
| Corner — a solved miter corner of the built wall | 8 px | square |
| Intersection — where two walls cross | 8 px | × |
| Midpoint — the middle of a wall | 9 px | circle |
| Perpendicular — a right angle from where you started | 8 px | circle |
| Edge — anywhere along a wall | 6 px | circle |
| Extension — the line a wall would continue along | 7 px | circle |
| Alignment — level with another point, horizontally or vertically | 6 px | circle |
| Axis — an exact 45° multiple from the last point | 12 px | circle |
| Grid | the fallback | none |
The tolerances are screen pixels, not millimetres, so they behave the same whether you are zoomed out over a whole site or in on a door jamb. A guide line is drawn for the snaps that need one — the extension ray, the alignment line — so you can see why the cursor jumped.
Jamb corners of doors and windows are snap points too, which is what lets a dimension chain pick up an opening without hunting.
The grid
Grid snapping is on by default and toggles with G or the Grid snap (G) button at the bottom of the toolbar. The button next to it, Show grid, only controls whether you can see it — the two are separate.
The module is 100 × 100 mm by default and is a project setting: ⚙ → Grid takes a pitch per axis, so a plan drawn on a 600 × 1200 planning module or a 300 mm masonry module snaps to that instead.
The grid snaps positions, not lengths. Both ends of a wall land on the grid; the distance between them is whatever the geometry gives. If you want an exact length, type it — see drawing to an exact length.
An exact snap is never re-rounded to the grid afterwards. When you land on a wall end, you get that point, not the grid point beside it — which is what makes wall joins meet exactly.
Why casual walls come out straight
When nothing more specific is near the cursor, an exact horizontal, vertical or 45° direction from the last point beats a raw grid point: within 12 px and 8° of that line, the direction is locked to it and the position is stepped along it by the grid pitch. Without that, a 4 m wall drawn at 1.4° looks straight and ruins the join later.
Shift makes it explicit and absolute: the direction locks to the nearest 45° regardless of what is nearby.
The reference point
You can measure from a point without drawing from it. With a drawing tool active and nothing placed yet, hover an endpoint, corner, midpoint or intersection and either pause for half a second or just start typing a digit. A diamond marker appears on that point, a dashed line runs to the cursor, and the readout now measures from the marker. Type an offset and press Enter to start there. Esc releases it.
This is shared by the wall tool, the fence tool and every polygon tool — areas, terraces, ceilings, ground surfaces, pools.
What this doesn’t do
- G does not turn all snapping off. It only disables the grid fallback; geometry snaps stay on, and they are the ones that make joins exact. There is no “snap off entirely” switch.
- A tool never snaps to what it is reshaping. Drag a wall’s end and that wall’s own corners and jambs are excluded — otherwise the wall would chase itself half a thickness at a time.
- Snapping is per storey. The ghost of the floor below is a tracing aid, not a snap target.