Compass for Whiteboard and Blackboard

Very sturdy. The axle can be tightened to your preference. Opens to about 200 degrees. There is no locking mechanism but it is unnecessary. The handle spins so that you can turn the compass while gripping the center rod comfortably. The chalk or marker holder uses a thick spring. It can hold things up to a regular Expo marker size very well and holds small things like chalk or pencils all right with not too much pressure. I attached some photos with my review - don’t let the single picture and bare description scare you, this is a solid product and I suspect the best on Amazon at this time.

This is the best I've owned: the compass locks so your measurement stays consistent; the 3 suctions leave the point free so you can match the marker point accurately and the suction cups do not erase the marker point you make; the twist handle makes turning the compass much easier.(I have had other brands break, the suction cup erases the marker point made on the board, there isn't a lock so your measurement is always off!)