Don't know if this has been posted....did not find in searches.
Just playing around looking for international MRs, I noticed many low fares can't be held online....usually call reservations and have to go to airport to ticket same day (am using CR systemwide vouchers.... I don't trust ticket by mail).
One evening, between 9-9:59 pm PST, I found that I could put reservations on hold at .bomb through the next day like a normal fare!@:-).
Had the next day to think about it (cancel the hold or hold the reservation again the next night) or take my time to go to SFO to ticket.
Not sure if this will hold all WEB or E-Fares, but has been useful to me not having to call reservations with a complicated itinerary.