[johnr]

One more guess. Hint one still looks to me like the plastic device moves back and forth along the smaller pipe with stopping pegs at each end. Now add spring/rubberbands from plastic to front and simple handle on back. You now have a shooting device for human player. Second hint is most likely a side rail. Side rail as in billards.
One more thing. Does anyone else see an optical illusion in second hint? The dark area looks like it is humped up,like a hill.