I made these corner brackets to hold my heatbed and glassplate together evenly without getting bent by the force of the levelling springs.
The top part has a slot for the glassplate and the heatbed as well as tension arms to keep the glassplate from moving during a print.
The bottom (NUT) part is designed to fit exactly around a prusa i3 aluminum cnc milled platform. It holds the nut in place, so in order to adjust the level of the bed, all you have to do is carefully loosen or tighten the M3 screws to lower or raise the corners.
This part could easily be customized to fit larger or smaller springs.
I printed these with black PLA at a 0.3 resolution and 30% infill.
The top and bottom part should be glued together (i.e. superglue).