Many, Many people, including some with a lot of experience confuse the terms of Lock vs Bolt. In a nutshell the Locks fire the gun, the Bolt/Bolts keep it closed.
The sidelocks are further divided as to whether they are Bar-Action or Back-Action. On a Bar=Action the Mainspring is forward of the hammer & when installed on the gun lies in a recess cut into the side of the bar. On a Back=Action the main spring is behind the hammer & fits into a mortise in the wood when installed. Note in both cases the spring is attached to the plate, this only states the relative position it occupies.