The sexton plays a large role in Act 4, Scene 2 with relation to the prisoners. He especially acts as a guide in the interrogation because Dogberry does not have a clue as to what he is doing. The first order we see the sexton give Dogberry concerning the prisoners is to bring them before the sexton so that they can be examined. Next, the sexton tells Dogberry that he does not know how to examine the prisoners and commands Dogberry to call forth the members of the security detail that actually caught the prisoners in the act of mischief, as we see in the lines, "Master Constable, you go not the way to examine. / You must call forth the watch that are their accusers" (IV.ii.29-30).
Finally, once it has become known that the prisoners, Conrad and Borachio, had accepted a bribe from Prince Don John to disgrace Hero so that she is rejected at the altar, the sexton tells Dogberry to tie up the prisoners and take them to Leonato. The sexton also says that he will go ahead of them and show Leonato the transcript of the examination, as we see in the lines:
Master constable, let these men be bound and brought to Leonato's. I will go before and show him their examination. (58-60)
Hence, we see that in Act 4, Scene 2, the Sexton first commands Dogberry to conduct the interrogation properly, and then when the sexton is convinced of the prisoners' guilt, he orders them to be bound up and taken to Leonato.