When conjugated in binyan hif'il, the yod of the verb root usually turns into vav, and it is now used as a vowel (O). examples: י.ר.ד: הוריד, מוריד, יוריד (to lower/ to bring down) י.ש.ב: הושיב, מושיב, יושיב (to seat someone) י.צ.א: הוציא, מוציא, יוציא (to take out) Now, if I may say, Im not sure the best way to study verbs is by memorizing the rules of binyanim. The other way around, I think learning the grammatical strutures is much easier to obtain by knowing how the verbs work in real life language. I think it's better to memorize a few specific verbs and their comjugations in all forms, and gain this intuition for Hebrew verbs more naturally. But whatever way you choose, good luck! :)