Please print this document on one side only.
I found a board painted red on one side.
両面 means 'both sides', while 片面 means 'one side/single-sided', as in 両面印刷 vs 片面印刷.
片面 describes something usable on only one side, the opposite of リバーシブル, which can be flipped and used on either side.
single-sided disk
Compound of 片 (かた, one of a pair) and 面 (めん, surface, side). The reading かためん follows standard on'yomi.