Abstract: An insert adapted to be positioned within an elongated channel member having a base portion and a pair of parallel sides, with the sides terminating in internally curled edges defining an open side forming a C-shaped channel, the insert having a width to be conformably received in said channel member either for longitudinal movement therein or to be positioned therein to receive the shank or axle of a caster or wheel, respectively. The insert may be either square in cross section and generally rectangular in shape or generally cylindrical with a pair of oppositely disposed grooves formed in the side surfaces of the insert to receive the curled edges of the channel member. The insert also may be provided with a body portion having a pair of oppositely disposed flanges extending from the body to form a generally rectangular outline, the insert being received in the channel member in a longitudinal manner.