When you need some fancy dice but all you have is a classic six-sided thing, there are ways you can use your die as if it was a different size - while still being fair!
This page lists a bunch of methods you can use to roll a d6 as something else, they do require extra rolls and/or arithmetic - but probably less than you would expect!
Sometimes a substitution may have multiple methods, the first will be the simplest method to learn, the others will have fewer rolls and/or a fixed amount of rolls.