yesterday i came across an old bloke broken down with a 1965 "HD" holden,these have a basic old straight six with a single down draught stromberg you see every where on old cars,anyway it would idle but cut out soon as you gassed it,anyway he had a tow truck coming and lived close by me so gave him my number to call me once he got it home,i went over and without taking the carb off the manifold pulled the main jet and removed the carb top,you can run these carbs with the top off if you block the power valve port on the top,took me 20 minutes with also checking the timing with a strobe,couldnt have done it with out this tool,i aint used it or touched a stromberg in over 30 years!the wide bent screwdriver gets the plug out in situ and doubles as the jet key lever,the jet key has two sizes one each end,just two flats in a hole more or less,the jet is too deep to grab even with pointy pliers,you need this key.