How to make sure which primary beam rests over the other when two primary beams intersect eachother?

when we intersect two beams which cross eachother , it is obvious that one beam would support the other one. bcoz in real life usually the longer beam rests over the shorter one when they intersect eachother bcoz the shorter one is more stable. So how do we make sure which beam of the two would rest over the other one when they intersect in staad.