402 b extending distally from the connection plate 300 b to which the bottom surface thereof is attached in the depicted embodiment the connection member 402 b extends distally over the locking plate 250 to a height adjustment receiving tube 420 at the distal end a retractable pin 404 b extends through the connection member 402 to interact with the locking hole 252 height adjustment receiving tube 420 has a bore running in a vertical direction and aligned locking holes 421 a and 421 b in the opposite sides thereof height adjustment bar 440 is a member sized to fit in the bore of the tube 420 extending vertically therethough which is placed in the tube 420 as depicted both height adjustment receiving tube 420 and height adjustment bar 440 may have square cross sectional shapes a plurality of receiving holes 442 allow the bar 440 to be secured at different selected heights in the height adjustment receiving tube 420 by rods 443 placed though the locking holes 421 a and or 421 b and the desired receiving holes 442 a hitch mounting plate 446 is secured to the bottom of height adjustment bar 440 and extends distally therefrom to support a mounting ball b or other hitch connection such as a hook or pin it will be appreciated that interchangeable connection ends 400 a and 400 b may be connected and disconnected to the system 10 by either the connection plate 300 and nuts as depicted with connection end 400 b or by a u201c quick connect u201d feature.