From Jo Hinchliffe on the Tindie blog:
We’ve all been there, poking a hot soldering iron at a component on a PCB and then the PCB shifts and components fall as your set up of tape and binder clips slide across the desk! Whilst PCB vice ideas are common, these Board Braces take a slightly different but very inventive approach.
The idea is pretty straightforward; each post is a large standoff with a screw clamp arrangement at the top of the post to hold your PCB in a groove. It’s a good approach as it adapts well to a range of PCB thicknesses and sizes. The base of the posts contain a strong magnet, so you have to work on a ferrous metal work surface (not supplied) and we like that that means the posts can accommodate PCB of many shapes and dimensions.