Abstract: The lap siding installation tool is a reusable tool that allows one person to easily handle and install horizontal lap siding on the side of a house or other similar structure. The preferred embodiment of this invention is a simple squared “Z” shaped bracket with spring mechanism that will grip the lower edge of the siding board to be installed. The upper part of the tool provides a “ledge” or “lip” on the backside of the board which will rest on the upper edge of a previously installed board. This “ledge” is in a defined position above the lower edge of the siding board to be installed such that a consistent overlap of the boards is maintained per the lap siding manufacturer's specifications. The board is then fixed to the structure in two (2) places along its upper edge, normally by nails or screws. The tools can then be easily removed by pulling outward on the lower edge of the board a small distance allowing the tools to be pulled downward off of the board.