a different way

Instead of inserting the stud into an open (inherently weak) plastic L-track channel and sliding it into position, this solution slides the clamp along the handrail onto the stud. This way the stud can be totally enclosed greatly increasing the strength of the part. The bottom of the clamp hooks on to the handrail and it flexes enough for the top to swing into place. Facing in opposite directions, the two parts are secure. You then slide them together on the stud and the washer and nut holding the attached device lock the clamp in position. The two ends are identical, so only one part needs to be printed twice. I was working on a more conventional solution and then this occurred to me this morning - final day! I am aware that every detail is not resolved but hope the lateral thinking appeals to the judges. And I thank the organisers for providing the impetous to fire up some CAD for the first time in a while - it's scary how much fluency can evaporate in just a few years!