The trailer hand valve should be used:

Question

The trailer hand valve should be used only to test the trailer brakes. It should not be used while driving because it may cause the trailer to skid.

Accepted Answer

Only to test the trailer brakes.

Answer

Regularly to activate the trailer brakes in all driving conditions.

Answer

Only in inclement weather when the trailer may skid.

Answer

Only if the trailer is carrying a load.