WHOLE CHARACTER
走zǒu
to walk; to go; to leave (走开); to move (钟表不走了); to leak (走气); to lose shape (走样)
走 is to walk and to go — on foot, away, or out of shape.
The header marks 会意, picturing a running figure; the modern upper and lower pieces are shown visually.
UPPER PIECE (土)
土tǔ
earth; soil
Repeated in 垚.
In 走: upper piece (土) The upper earth-like piece; no historical role is claimed.
LOWER PIECE (THE RUNNING-FOOT FORM)
龰zhǐ
a bound foot/stop piece (written variant of 止)
A bound bottom piece appearing under other parts in several characters; a dictionary variant shape, not taught as a standalone word.
In 走: lower piece (the running-foot form) The reduced running-foot form, shared with 是.