A metal casting bolted or spiked to the sleeper, featuring a jaw that grips the web and lower loop of a bullhead rail. A wooden or steel key is driven between the rail and the chair to lock the track in gauge. North American railroads favor flat-bottomed rail secured by tie plates, making chairs primarily a feature of British trackwork or older historic installations.
Heard on the job
The track gang is driving new keys into the chairs on the heritage line.