Scale Model Ship Waterline Scribe

I use this scribe to mark waterlines on the hull of a model ship or boat. Clearly, it can be used for other purposes where an adjustable-height scribe is needed.

The arm has a hole/slot for a 5/64 (2mm) lead or blade; I found these among the spare parts for compasses at the local art store. The base, arm, and nut have an M5x0.8 thread. I used a 100mm threaded steel rod in the photos; I found a nylon or printed PLA rod is too flexible.

The base is hollow as I thought I might want to add some weight to the base, but I haven't yet needed to do so.

I printed the parts in PLA at 0.2mm structural with default slicer settings. No supports are needed with proper part orientation.