背床板

bēichuángbǎn ㄅㄟ ㄔㄨㄤˊ ㄅㄢˇ

    • to lie in bed
    • to sleep

Character by character

Saying俗语俗語

Idiom惯用语 · Rarely used now

Literally
carry the bed board on one's back
Meaning
The book glosses it as lying in bed, sleeping. Colloquial.

Sources