Embodiments of a pusher device may include a frame, guide rails coupled to the frame, a carriage slideable along the guide rails, and a linear positioner coupled to the carriage and frame and operable to move the carriage along the guide rails. Two or more lugs may be mounted to the carriage and rotatable between a resting position, in which the forward ends of the lugs can contact the transverse supports of a tram above the carriage, and a lowered position in which the lugs can pass below the transverse supports. In the resting position, the longitudinal axis of each lug may be inclined from rear to front, such that the lugs contact the tram with the front end (as opposed to a longitudinal side) of the lugs. The lugs be generally triangular, trapezoidal, or concave polygonal in profile. Corresponding methods and systems are also disclosed herein.