Hidden Glidebolts:

Not all glidebolts show. Unless you are familiar with the make and model of a grand piano, it might be worth the extra effort to pull the action enough to have a look at its underside.

Keys must clear a protruding bolt or provide space for screwdriver access to a slotted bolt. In some well-known keyframes, one of the glidebolts will be offset toward the back to facilitate the placement of that clearance. But there are keyframes, like the one shown above, that simply offer no access except by key removal. 

Bedding the Cheekblocks:

What are the functions of a cheekblock? In a Steinway grand, a cheekblock provides three important services: positioning the action in-and-out for tone, side-to-side for soft-pedal shifting, and up-and-down to complete the crowned frontrail bedding. Arguably, there is a fourth function: securing action to keybed for when the piano goes on its side. And, of course, there are the casepart functions to hold and stop the fallboard. In any case, the guiding and holddown functions conflict, with downward pressure on pins that must slide freely and silently side-to-side.