Abstract: A walker which comprises a pair of interconnecting side frames. Each of the side frames includes a pair of upright legs and a hand grip bar connecting upper end portions of the legs. A caster is adapted to support each leg. A spring is mounted in association with each caster to urge the leg associated therewith to a raised position in which the lower end of the associated leg is spaced above a surface on which the casters run. The springs yield when weight is applied to the bars to cause the lower ends of the legs to engage the supporting surface to lock the walker in position.