[Test-Equipment] Risers on your workbench

[davec]

The "2nd shelf" above your work bench.

My workbench is a purpose-built (don't know the brand) steel chassis 
with plastic-top laminated particle board work surface. In the back 
corners are two square 2-inch holes (that extend into the rear legs 
of the bench) intended for risers.

How would you utilize these holes? Have "L" supports made from 2-inch 
square steel tubing? Or wood? Should the shelf be parallel to the 
work surface? Slightly canted downward? Other features?

Help in planning this extension of my work area would be greatly appreciated.

Thanks,
Dave