Your scooter takes you to the barracks, drops you off, and then goes in reverse all the way back home in the opposite direction.
Your scooter going in reverse and leaving you here is opposite of what you want. You want to ride it back home when you're done, so you stuff the wheels with Gak (ぎゃく). If you don’t know what Gak is, check out this Gak commercial.
Currently there are no similar looking kanji which exist in the WaniKani learning system