In reply to ColinVern:
> (In reply to Landy_Dom) , might be a health and safety thing (though that sounds bonkers) for liability etc.
Not that bonkers actually. It's easy to over tighten and crack holds, especially on a featured fibreglass wall, the cracked parts then fall off and brain someone. It's also pretty easy to drop allen keys (yes even with a clip) which could be nasty on a busy night. I've also seen occasions when customers moved holds to change a route.
For these reasons most walls prefer to do it themselves.