In our office we have a suspended ceiling that we wanted to attach stuff to. Firstly we wanted a curtain rod to partition off a bit of the open plan. And later two small lights for a disco ball!
The first version worked quite well for the curtain rod, a couple of the small hooks got broken off but I made plenty enough. But it was a design flaw with the ABS-plastic too brittle.
I used the same design for the lamp holders, but it became obvious that it was too weak and a redesign was necessary.
The result is a three part holder. Two parts that grip around the rail and each other like puzzle pieces. and a third that are a bit tapered that squeeze them together. And it worked perfectly!