Shower rail holder

[slystallone]

Is anyone familiar with this types of shower rail brackets for holding the rail upon which the shower head holder slides up and down on and how to remove these? I could just get a drill I guess to get at the screw underneath, however as can be seen below there is a hole of some sort, which appears not to have a screw head that I can see and maybe it can be removed in an easier way then just drilling through it.Any advice would be greatly appreciated

Edited Wednesday at 21:14 by slystallone

[Nickfromwales]

Allen key may be the way, as some are held on by grub screws.