spawn box next to each other over and over for ever? Swift

HI im trying to make a game where theres a character and he jumps up on boxes like this

but i cant seem to get spawning down, all i need is to use the runblock function to keep spawning boxes but next to the previous box each time if you know what i mean, just make the block coming in next to the previous block so makes stairs i can get the height randomized so i just need them side to side thank you