The slot in a standard panel is set by bar pitch, which is chosen for drainage area and for strength. Nobody chooses it against a heel, a cane tip or a castor, and the result is a slot width that catches all three.

Heel guard grating closes the slot down. The drainage area lost by narrowing each slot is recovered by having more of them, which means the panel takes the same water and carries the same load as the standard version it replaces.

The cost is steel and machining. More slots means more bars and more cutting, so a heel guard panel is heavier and dearer than the standard panel of the same size. It is worth it precisely where the public walks and not worth it in a plant yard where only staff in boots cross the run.

Specify it by where the drainage crosses a walking route rather than by the building type. A hospital has service yards where standard grating is correct, and a factory has an entrance where it is not.