The "common escapements" are those that are found in the domestic clocks that are most frequently found in a clock repairer's workshop. The average clock repairer is very rarely called upon to attend to a three legged gravity escapement or a "Graham grasshopper" (my earlier book "Practical clock escapements" deals with those). A book that deals with the design of the escapement only is very useful, but what a repairer really wants is a quiet word with the person who mauled the clock last and some useful information about what to do to repair or replace the sad result. This book describes what the escapement should look like, how it should operate and practical measures to achieve those aims. It also explains the effects that different proportions of the movement have on the design of the escapement and points out the errors that arise as a result of assuming that all escapements are "square," ie. linking the pallet arbor centre to the tip of the tooth that is about to be touched by the pallet, from there to the wheel centre and from there to the tooth that has just been released, and back to the arbor centre again - will trace out an approximate square. Most British authors appear to make this assumption, because long case and bracket clocks typically have square escapements, yet American and Continental clocks very frequently are anything but square. As a result repairers find themselves in difficulty when dealing with escapements that do not conform to the British pattern. My hope (and expectation) is that this book will make the life of the average repairer a little easier.