The Grid defines:
- How parts snap to the virtual Ground when Snapping is on
- How parts move when Snapping is off
- The steps used with the W A S D keys, whether Snapping is on or off
The Grid doesn't define how parts connect and move relative to each other when they're connected, and Snapping is on. For instance, a clip will glide smoothly on a bar no matter what level the grid is set to.
The Grid is controlled from the toolbar:
Coarse: horizontal step is one stud, vertical step is one brick
Medium: horizontal step is ½ stud, vertical step is ½ brick
Medium-plate: horizontal step is a half stud, vertical step is one plate
Fine: horizontal and vertical steps are one LDU (LDraw Unit)