I have been using the 'pin' on three Shimano chains(10 speed) and the only thing that was not clear was which side of the chain should I use when inserting the pin? I decided on inserting the pin on the non-drive side of the chain and breaking the pin off on the drive side. This lets the non-drive side that runs near the cassette be perfectly flush, when you break off the pin on the drive side it is not perfectly flush.