Rashi on Exodus 30:4/רש"י על שמות ל׳:ד׳

1צלעתיו Here this word must signify “corners” (not “sides” as Rashi explains in Exodus 25:12), as it is translated in the Targum, since it is stated afterwards, על שני צדיו, “upon the two sides of it”, so that the phrases mean, “the two corners that are on its two sides”.

2והיה (lit., “and it shall be”, not “they shall be”) — i. e. the making of these rings (this ring-work) shall be (shall serve) —

3לבתים לבדים FOR PLACES FOR THE STAVES — i.e. the ring shall serve as a place for the stave (cf. Rashi on Exodus 25:27).