Vehicle seat mounting devices

A vehicle seat mounting device comprises a first frame and a second frame mounted for relative sliding movement by guide rails attached to one of the frames which are engaged by rollers on the other of the frames. An intermediate frame within the device is connected to the first frame by a position adjusting device operable by a first actuator whereby the first frame can be locked to the intermediate frame in any one of a plurality of different selected positions. The intermediate frame is connected to the second frame by springs to allow resilient relative movement therebetween. A lock-out device is operable by a second actuator to lock the intermediate frame to the second frame. A common operating member coupled to the first and second actuator is movable between a first position in which the first and second frames are movable under the constraint of the springs, a second position in which the first and second frames are locked together and a third position in which the springs are locked out and the first frame is adjustable relative to the intermediate frame.