It can be difficult to get an even layer of metal coating when sputter coating a sample with steep sides, a rounded lower surface, or one that doesn't make complete contact with the surface of the specimen stub. It can be particularly difficult to get sputtered metal in under the sample, and so an insulating sample (like most polymers and biological specimens) may have little or no electrical path to ground. This results in charging, and increased chances of specimen heating and beam damage in the SEM.

These stub holders were made to fix that problem. A couple of metal shelf brackets, which slide into pegs and support the shelf, were modified. The brackets are small 90° angles with a hole in one face and a peg on the other face. To modify them, first the 90° angle of the bracket is bent slightly past 90°.