Shims are a useful method of extending the life of a rail joint and can be an effective way to manage the early stages of joint fatigue like worn fishing surfaces and dip angles.
They work by taking up the wear between the fishing surfaces of the rail and the fishplates which helps prevent the rail ends from becoming crippled.
Shims cannot be used on insulated rail joints and will not cure crippled or battered rail ends. In addition they cannot be used to
correct mismatched rail sections.
This video shows you how to correctly shim a rail joint
