This is a bracket or brace for the corners of a workbench. It has three slots for 2 brace boards and 1 table leg. Below is an example image of the workbench and a materials list.

Materials for:
2'D X 5'W X 3'H Workbench

(5) 2 x 4 x 8' lumber
(2) 24" x 60" shelf surface

2'D x 8'W X 3'H Workbench

(7) 2 x 4 x 8' lumber
(2) 24" x 96" shelf surface

Additional hardware

Leg Screws- x48 #10 x 2-¾" wood screws

Surface Screws- x16 #10 x 1-½" wood screws