having a number of tool boxes ( i'm a central heating engineer) for work i have my sparks box, gas box, soldering box, masonary box, drill box, some have duplicates in one or more boxes but this way i know that if i pick up my soldring box everyhting i could ever need would be in it.
same goes for my bikes 3 bikes ( two metric one imperial) just finished putting together a box for my beta. i bought a set of spanners and allen keys, toched every fastner with them then set aside all the spanners/ keys not used so they dont go in the box. added a flat blade screw driver a phillips ( size 2) driver. pliers ( with a cutting edge) i have air filter cleaner and oil, two stroke oil, gear oil, wd40, contact cleaner. tyre pressure gauge.
that all fits in a nice biscuit tin and comes to every trial not needed anything else yet...