Aluminum bed nut holder

I have a aluminum plate (http://reprap.org/wiki/PCB_Heatbed/Aluminium_Bed_Mount_Plate/Borosilicate_glass#Aluminium_Plate) and some times when leveling the bed when i turn the screw it also turns the nut at the bottom, but if you use this nut holder in each corner of the plate the nut will never turn again.

The nut is placed 5.5 mm from each edge of the corner plate.
The plate is 2.7 mm thick

I remove the corner because my plate corner is not perfect.