Object snap
The cursor sticks exactly to the important points of an object.
The points it sticks to = endpoint, midpoint, the centre of a circle or arc, a point object, an intersection, the centre of a shape, and text (insertion point, the four corners of the box, and the centre).
- The centre of a shape = the middle of a closed shape (a lilac □ with a dot). Rectangles, polygons and closed polylines announce it. For example, drawing a bolt hole at the heart of a hexagonal nut — you can snap straight to the centre. ⚠️ It is a point in mid-air, so if a real point (an endpoint, say) is nearby, that one is announced first. Press Tab and you can reach it.
- Besides its two ends, a spline also snaps to the fit points you clicked yourself (the very points you made when you drew the curve). It does not snap to the control points: those are weights floating off the curve, so catching them would mean nothing.
Where candidates overlap, Tab switches between them.
The スナップ (Snap) toggle on the bottom bar turns it on and off.
The constraint toggle (free / ortho / polar)
Each press of the constraint toggle on the bottom bar moves to the next one.
- Free = no constraint. Draw as you please.
- Ortho = right angles only. Horizontal and vertical. F8 switches it too. Hold Shift and it is reversed for as long as you hold.
- Polar tracking = a guide line every so many degrees. Right-click the toggle = change the step (45, say). You can also type POLAR 30 in the Command Line.
Where it takes effect
It works in any tool that already has one point down.
Line, polyline, move, copy, stretch, grips, circle (centre to radius), three-point arc, ellipse, spline, the corners of a hatch, dimensions, the elbow of a leader, arrays, isometric, the axis of a mirror, and unit scaling.
It does not work on the very first point (nothing has yet decided what “horizontal” is measured from — this is the convention across CAD).
Where it does work, the prompt beside the cursor says either “F8＝直交” (F8 = ortho) or “直交ON＝水平・垂直だけ” (ortho on: horizontal and vertical only). If you cannot go diagonally, look there.
※ It is deliberately not applied to the far corner of a rectangle or of a paragraph of text (constraining that corner to right angles would leave you able to draw only squares).
※ Rotation constrains an angle, not a point (ortho on = steps of 90°).
The laser (⌥ Option)
While ⌥ is held, the lines you can point at light up and a note appears.
For apparent intersections (APPINT), ⌥-click adds and removes reference lines one at a time.
Midpoint between two points (M2P)
An interruption that takes the middle of two points you indicate and hands it to the tool you are using.
While a tool is asking for a point (a base point, an insertion point, the first point…), type M2P in the Command Line (MTP or 真ん中 also work), indicate two points, and their midpoint is passed straight to the tool.
For example, text in the middle of a box in the title block: catch the text by the centre of its shape and move it → M2P → the two opposite corners of the box → it lands in the middle.
Snapping works on each of the two points, so you can use intersections and endpoints exactly.
To stop: right-click or Esc (the tool itself carries on).
Turning the prompt and the distance field on and off
- GUIDE = turns the prompt beside the cursor on and off.
- The 距離DYN toggle = turns the distance field beside the cursor on and off.
Turning them off loses you nothing. Choose whichever suits you.