The author of Instructables, under the nickname mozzwald, talks about a home-made analogue of the Martin SMT magnetic circuit board holders for a printed circuit board. They are easy to manufacture. do it yourself and can be used as a "third hand" when soldering and soldering components.
For each holder, the master prepares a bolt (M6, pitch 1 mm, length 55 mm), spring, washer (not shown), sleeve and magnet (diameter 12 mm, thickness 3 mm):
In each of the aluminum disks (diameter 50 mm, thickness 6 mm), the master makes a recess for the magnet and a hole for the bolt, where he cuts the internal thread. It is not very reliable - a steel bolt, a threaded disc - aluminum.
Paste magnet:
Screws in a bolt and notes where to saw off. Sawing off.
From a bolt, spring, washer and sleeve assembles this design:
Turns the disc magnet down, compresses the spring, screw in the bolt, and you're done. The remaining three holders are made in the same way.
Now it’s enough to magnetize the holders to any steel base, and then slide them so that it is convenient to clamp the board between the bushings and the bolt heads.
The ability to move the holders allows you to clamp irregularly shaped boards, which is quite common in electronics, modern and not only. Proposed homemade provides greater rigidity than the classic "third hand", where the clamp is only one. Even a large board hardly bends after a soldering iron.