This is a Bed Clamp I made for my Kossel Mini. Bed can be levelled if needed with the adjustment nuts and locked down with another set of nuts. It's designed for my 220mm diameter heated bed but should work with most other bed sizes as well.
You need to print 3 bases + 6 nuts.
Only needs 3 x M4x8 screws to fix the 3 clamps down onto the beams.