Abstract: Apparatus and method are disclosed for enabling a single operator to correctly position and clamp a power tool, such as a drill, onto a rail or beam-shaped workpiece. The apparatus has an adjustable clamp, comprising gauge blocks that provide snug multi-point stable contact with the workpiece in cooperation with a movable guided jaw. A sight hole ensures correct positioning of the clamp by direct viewing of a mark on the workpiece. A thrust bearing positioned between the movable clamp jaw and a clamp locking nut facilitates clamping and unclamping in repeated use and permits the application of a clamping force sufficient to carry the weight of the entire apparatus, including a power-tool attached to the clamp. The drill, including a hollow centrally-lubricated annular drill bit, is manually guided into the workpiece along guide rails attached to the clamp in the same plane as the drill axis for maximum stability during operation in any orientation.