The Independent Post Cap system means that the post is held very securely and, crucially, it is held separately from the main beam.
The independent post cap runs on two rails, one on either side of the mast, which allows free movement of the beam through the cap and means the cap does not lift off the stake on full stroke.
This allows the full force of the hammer to be transmitted even when working at an angle, making for extremely easy, accurate and fast driving of posts.
For additional stability the stake is held by means of spike on the underside of the cap.
The images below show the post cap in place on a very large and heavy post being driven with ease into hard stony ground, in around 2 minutes, by the Model 4 Fence Post Driver. You can see the process in the video below.