Options for positioning the cursor

Snap To Grid

1 means that your cursor will snap to the grid lines, 0.5 will also snap halfway between them, Off will not snap to the grid lines.

Snap To Endpoint

On will snap to the ends of previously drawn lines or arcs, Off will not.

Snap To Angle

Whether the line and arc tools should snap to particular angles in increments of 1, 3, 5, 15, 30, 45, or Off to disable.

Snap To Length

This is so that angled lines can snap to particular lengths. 1 corresponds to the size of one grid cell. Can also be 0.5 or Off.