The Drafting Compass is a tool added by BiblioCraft that allows you to place
waypoint markers on maps in Map Frames. When you right click on the map it will bring up an interface that will allow you to name the marker, colour it one of 16 colours and cancel or accept.
To edit the marker shift right-click on the marker with the drafting compass and
it will bring up the interface again with the extra option of removing the marker as well. If you have trouble clicking the marker as it can be quite precise, point your cross-hairs at the base of the marker.
Right clicking on a marker will tell you in the chat window the world coordinates like this: Waypoint Name @ X = -100 Z = 100