This isn't only an Indian problem Steve and others although on that example, the examiner seems to have ignored the bleedin' obvious! This was a regular problem with No4's (and 5's) and even today, with the SA80. On the No1 and 4, the breeching up gauge indexed the flat of the knox form with a parallel gauge that went into the body and.......... and whatever it did, it didn't! Because if the flat of the knox form was just a gnats knacker (remember that word, it's a particularly Britishicon Army technical phrase, indicating 'a little bit less than a little bit.....') out, then the foresight would lean over. Not a lot (but a LOT in some cases.....) and zeroing would be a nightmare. As a result of that, while the EMER quoted the official method, everyone the whole world over used a sheet of glass and vee blocks.