This paper discusses the theoretical analysis and the experimental validation of the step and stair climbing capability of WheTLHLoc, a small-scale hybrid locomotion robot for surveillance and inspection. The architecture of this robot combines two tracks, two rotating legs, two actuated wheels and two passive omni wheels. The robot is capable to perform different locomotion modes: wheeled locomotion on flat and compact grounds, tracked locomotion on soft and yielding terrains, mixed use of tracks, legs and wheels to overcome obstacles. In particular, the process of step and stair climbing is analyzed considering static stability and non-slipping conditions. The experimental campaign on the first prototype has confirmed the effectiveness of the proposed climbing maneuver and the operative flexibility of the WheTLHLoc robot.