I believe they are called a compass (Sounds the same as the thing you use to find your direction). A sharp tip on one end, and a pencil holder on the other, with an adjustable wheel/screw to change the size of the arc/circle.
A protractor is one of those half-circle devices used for determining angles.
And those were Killgar's learning tips for the day![]()
Yup thats the thing right there. No permanent damage was done but he still had to go to the hospital. This was a good 5 years ago though. Apparently I'm not nearly as old as a lot of you guys on here lol.