Guides on Guides

When I create a primitive by clicking to get the dimensions dialog box, I noted that, if the click is on a guideline, a second guideline appears. It’s brown with two anchor points and aligns with the guideline in question. One end of the mini-guideline lays at the point I clicked on the guideline, the other end lays on the guideline control node.

What is that? What is it’s use?

Ooops. What is “its” use. You think I’d know better after writing a thesis.

The second guideline is a snapper. It indicates that the click was snapped to the guideline.