A customizable storage rack replaceably mounted either on a top or on a bottom of a shelf, stores handguns, and positions the handguns at customizable distances from each other. The customizable storage rack includes a body, mandrels, and attaching apparatus. The body is replaceably mounted either on the top or on the bottom of the shelf. The mandrels are replaceably attached to the body, store the handguns, and position the handguns at customizable distances from each other. The attaching apparatus is operatively connected to the body, and replaceably mounts the body either on the top or on the bottom of the shelf.