These are a mash-up of mdkendall's Parallel Jaw Pliers and P-atix's Self Lock Pliers. I printed them as tubing pliers, but they can be used to hold just about anything on two flat faces instead of on vertexes like most pliers or wrenches do. They use 4x M3-6mm screws to hold the jaws, and an M3-8mm screw to be the pivot.

Update 7/30/22:

They're not quite as robust as I had hoped. They're great for holding thin, pliable things together (basically like a bag clip), but aren't that effective at actually pinching off fluid tubing like I had hoped to use them for. I think I could probably get better engagement on the teeth, have the handles further apart so more force is applied when locked, and possibly taper the actual clamping area of the jaws to a point instead of flat. Keep an eye out for an update… eventually!