crosspiece vs rundle

crosspiece and rundle both are nouns.

Word	Noun	Adjective	Verb	Adverb
crosspiece	Yes	No	No	No
rundle	Yes	No	No	No

As nouns, rundle is a hyponym of crosspiece; that is, rundle is a word with a more specific, narrower meaning than crosspiece:

Other hyponyms of crosspiece include crossbar, rung, spoke, round, rung, stave, cross thwart, thwart, transom, traverse.

crosspiece (noun)	rundle (noun)
a transverse brace	one of the crosspieces that form the steps of a ladder
a horizontal beam that extends across something