The tool rest is where the metal item will rest as you grind it. The rest should be secured in place so there is a 1/8 inch (3 mm) space between it and the grinding wheel.
[header] How to use a bench grinder [title] Perform a safety check before turning the grinder on. [substeps] Make sure the grinder is tightly secured to the bench. Check that the tool rest is in place on the grinder.