Yeah it’s got a bit at the bottom you can attach a clamp with.
My dad was a building surveyor, and he’s also got a box of dried up Rapidograph pens in a cupboard which he’s convinced he might use again some day. My dad used to spend a lot of time swearing at them in the 80s because they blocked up if you looked at them, and there were loads of tricks like putting them in boiling water and hitting them against tables to get them working again (or repeatedly patiently taking them apart, cleaning them with alcohol and then putting them back together). I think they dramatically improved the ink at some point.