Reversing polarity for the birds lol!

[Anonymous]

hello everyone, i am intrested in making a reverse loop on my layout, i dont not have much room my layout is 2x4 but i have the atlas book and i should be able to have enough room however i am stumped on the saying reversing polarity i know that i will need insulaters but do i have to cut the track or could i use the insulaters as connecters, if i use the insulaters should i be fine or is there anything else i will need to do, and once again does that have anything to do with reversing polarity?

P.s. does it matter what type of elcectrical unit i use, could i use just a single with all the metal plates and screws or should i use a double?