It's the difference between in the class room as snotty nosed apprentices and what the real Armourers taught you once you were out in the real world. Another similar 'tool' was the tool designed, probably by Biffo the Bear or Alice in Wonderland somewhere for removing the L1A1 rifle extractor, stay and spring. Thumb levers, axis pins, pins split joints. What an absolute palava. When every Armourer knew after the first time he used it that the very best tool was the tough little pin actually made for the job, fixed to the combination tool. Both would/could let the stay and spring fly out into the great unknown so you just pointed it towards your waist so that if the spring and stay did fly out, it just flew into your overalls!