Any trick to installing seats? Mine stick once tightened

[Tidybuoy]

I just bought a set of 964 seats for my '74 911. Everything seems to be the same except once I torque down the bolts, the seats will barely slide forward/backward.

I'm wondering if there is a trick to installing or do these need some type of spacer. Or, maybe the rails have to be aligned just perfectly (like a door or window) to function correctly. In fact, my original '74 seats were difficult to slide forward/backwards and so I've been thinking that there is a missing spacer or something. If I loosen the bolts 1/2 turn each, the seats slide perfectly but I don't like the idea of having loose bolts on the seats.

Any advice would be great.

[NICE 69 S]

Bolt the rails on without the seats. Place a piece of glass or a flat piece of wood so it covers both rails and you should be able to see where the problem is. Both rails should be flat against that surface. If one end of a rail isn't sitting on the glass, shim it up until both rails are sitting perfectly flat against the glass.
Bob B

[cmonref]

The tightness might be from the rails moving slightly while being torqued down. I tighten the rear bolts first, as snug as possible but with the front ends of the rails able to still move slightly sideways. Then tighten the front ones. Move the seat fore and aft. If too tight, loosen ONE front bolt and move slightly to one side, and retighten. Move the seat again. If it is MORE tight, move the same front bold slightly the OTHER way and retighten. Move the seat again. Keep playing with one front bolt at a time until the seats moves easily.

[john walker's workshop]

i've had to shim the rails off the floor with some washers occasionally, so they didn't bow.

[Tidybuoy]

Thanks all. I think I know what to do.