The bumper spike acts as a pivot between the engine body and guide bar. Apply the bumper spike’s lower tip at the intended hinge width. Press with your left hand against the front handle while lifting the rear handle with your right hand. Saw with a pulling chain until you have achieved the appropriate hinge width. The hinge must have a uniform thickness. Do not forget to insert the felling wedge into the saw cut after you have sawn just over half of the diameter.
You can also saw from the opposite direction using a pushing chain and apply the upper tip of the bumper spike. Sawing usually becomes more irregular and the engine resistance is greater.