Shemot 26:20-22

Orthodox Jewish Bible

²⁰ And for the second wall of the Mishkan on the tzafon (north) side there shall be twenty kerashim (planks):

²¹ And their arba’im sockets of kesef; two sockets under one keresh (plank), and two sockets under the next keresh (plank).

²² And for the back of the Mishkan on the west, thou shalt make six kerashim (planks).