Someone pls help me to understand what the lock and key theory is for how enzymes work. (use diagrams if it helps)

according to this theory both enzymes and substrate possess specific shapes that fit exactly into one another.This model explains specificity.

general example when we open the door of our house we use a specific key to open the door not all keys will open the door of our house.In this example the key is substrate and the door or lock is the enzyme that fits into specific substrate.