DIY METAL/WOOD SCRIBERS AND GRINDER HOLDER!!!

[Frank S]

Those are generally called trammel points. By drilling into the end of the bolts and inserting a tungsten from a tig torch that has been sharpened to a point will stay sharp a lot longer than a common bolt will.
Set the edge of the trammels on opposite legs of a framing square to use as layout guides for marking stringers for stairs