They prevent parts from shifting or spinning during drilling.

The Precision Backbone: Inside the Versatility of Angled Plates (1.43")

In the world of precision engineering, securing a workpiece at the perfect 90∘90 raised to the composed with power

They provide a stable, square surface for accurately marking out parts from a face datum.

(e.g., 304 vs. 316 stainless for the angled plate)