Pardon my ignorance but can someone explain the difference between a liner lock & a frame lock. I always tought they were the same.
Pretty much. Remove the scales from a liner lock and presto, you have a frame lock. The only inherent difference is whether the lock bar is covered or exposed.
In practice, frame locks are commonly thicker than liner locks, since for equal overall handle thicknesses the frame lock thickness is that of the liner lock's scale and liner combined.