above and below; top and bottom
A set phrase referring to the upper and lower parts, or things located above and below. Often used in spatial descriptions or when comparing two positions.
I placed the books separately on the top and bottom shelves.
In this picture, the balance between the top and bottom is poor.
Compound of 上 (うえ, 'above') + と (and) + 下 (した, 'below'). The reading した becomes voiced to した due to rendaku in this fixed phrase.