Abstract: A ladder structure in which a plurality of extruded aluminum steps are secured to spaced, vertically disposed side rails, the rails seating in slots in the ends of the step. The slots are closed by end caps, and a screw extends through the end cap and rail into a screw receiving recess in the step. The step contains two laterally disposed screw receiving recesses, and screws extend through the cap into those laterally disposed recesses and, along with the first screw, secure the caps firmly on the end of the step and the step firmly in place on the side rails. The ladder has particular application to vehicles such as motor homes, vans, campers, pickup campers and boats, as well as other uses where the ladder is permanently installed.