A custom tool accessory to hold a tool, the custom tool accessory including a body, at least one tongue disposed at a first side of the body, at least one tongue receiving groove disposed at a second side of the body opposite from the first side of the body, and a tool holding portion disposed on the body to hold the tool. At least one magnet is attached to the underside of a metallic base plate that is in turn secured to the underside of the body. A retainer surrounds the at least one magnet and also underlies the area of the bottom of the base plate that is not covered by the at least one magnet.