Usage
Click the use angle toggle button to activate it. This toggle button cannot be deactivated by clicking it again. You have to select use x value, use y value, use z value, or select another menu to deactivate it.
The angle can be set with the make value button. To actually use the angle, click the snap to value button and select a point.
Comments
The angled line for this toggle button can be changed with the make value button. To actually snap to the angled line, click the snap to value button and then select the point that you want to snap to the angled line. The point will snap towards the angled line along the normal of the angled line that runs through the selected point. The snap will affect two coordinates of the selected point. Which coordinates depends on the window view in which the angle was set.
See also
use x value, use y value, use z value, snap to value, make value