For centering – or re-centering – the stone, we offer a Target Dop. It is a flat dop with a series of concentric circles machined into the Flat face. It functions as its name indicates, as a Target Dop – a visual aid, used in a Transfer Fixture to align the stone on center to the working Dop. It is a step-by-step process – and we suggest that on Google you enter “how to use a Target Dop” (there will be several instructions).