You buy a cheap set of feeler gauges helt together with a bolt ( or rivet )
Remove all but the 0.002"( points opening ) 0.012" ( max points lift) and .020 or .025 ( for plug gap, depending upon the plug )
Replace bolt put housing in a vice and aquash the outer cover so the remaining leaves are tight
Job done, cost about £ 2.00

Even better is to cut the ends to a blunt V so they get into the magneto easier .