The business of the two-act, which secures its effects by actions that are often wholly without words, makes the two-act more difficult to time than a monologue. Furthermore, even if the time-consuming bits of business were negligible, the precise timing of a two-act by the author is not really necessary.
Precisely as a monologist can vary the length of his offering by leaving out gags, the two-act performers can shorten their offering at will—by leaving out points. Hence it is much better to supply more points than time will permit to delivery in the finished performance, than to be required to rewrite your material to stretch the subject to fill out time. All you need do is to keep the two-act within, say, twenty minutes. And to gauge the length roughly, count about one hundred and fifteen words to a minute.
Therefore, having arranged your points upon separate cards, or slips of paper, and having shuffied them about and tried them all in various routines to establish the best, choose your very biggest laugh for the last.  Wherever that biggest laugh may have been in the sample routines you have arranged, take it out and blend it in for your final big roar.
 See description of card system, Chapter VI, section III.
Remember that the last laugh must be the delighted roar that will take the performers off stage, and bring them back again and again for their bows.
IV. MAKING THE MANUSCRIPT A STAGE SUCCESS
The manuscript of a two-act is only a prophecy of what may be. It may be a good prophecy or a bad prognostication—only actual performance before an audience can decide. As we saw in the monologue, points that the author thought would “go big”—“die”; and unexpectedly, little grins waken into great big laughs. There is no way of telling from the manuscript.
When you have finished your two-act you must be prepared to construct it all over again in rehearsal, and during all the performances of its try-out weeks. Not only must the points be good themselves, they must also fit the performers like the proverbial kid gloves.
More two-acts—and this applies to all other stage-offerings as well—have started out as merely promising successes, than have won at the first try-out. For this reason, be prepared to work all the morning rehearsing, at the matinee and the night performances, and after the theatre is dark, to conjure giggle points into great big laughs, and lift the entire routine into the success your ability and the performers’ cleverness can make it.
Even after it has won its way into a contract and everybody is happy, you must be prepared to keep your two-act up-to-the-minute. While it is on the road, you must send to the performers all the laughs you can think of—particularly if you have chosen for your theme one that demands constant furbishing to keep it bright.