Abstract: A vertical body member has a slot leading down from the upper end thereof for receiving and supporting a piece of siding to be installed. The slot has a depth that determines the overlap of a piece of siding and is defined at the rear by a wall terminating in its upper end in a rearwardly turned hook portion that can hook over the top edge of an installed piece of siding for supporting the body member and a piece of siding to be installed. The hook portion has a selected rigidity such that it will support a piece of siding that is being installed but also has a resilience that allows it to straighten out when the body member is pulled forcefully downwardly whereby the rear wall and hook portion can be slid out from between a previously installed piece of siding and a piece of siding just installed. The hook portion has memory characteristics such that it will reassume its hook shape after being removed from between the siding pieces.