I use these magnetic rails: https://www.amazon.com/gp/product/B00401FZDW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I keep the rail in a canvas tool bag with everything else and they still stay put, may shift on the rail a little, but they never had one fall off. The black pegs unscrew allowing you to slide them on the rail and space them as needed. They make them with different sized black pegs depending on the drive to help keep them centered.