anybody know how to fit them (no instructions supplied)

One has a larger diameter hole than the other, which is which?, and which bolts do you remove to fit them?
There also appears to be 2 allen bolts on each steel arm, I presume these tighten up against summat?
Help, anyone! In the meantime I'll mail the seller for advice
Cheers
Mr t00lkit.
p.s.
Del, Mrs t00lkit (velcro butt) has read your notes and if we pass by your way, you're in for it big-time!
