The "Civil Litigation Management Manual" published by the US Judicial Conference directs that these motions be filed at the optimum time and warns that premature motions can be a waste of time and effort. The significant resources needed to prepare and defend against such motions is a major factor which influences litigants to use them extensively. In many cases, particularly from the defendant's (or defense) perspective, accurate or realistic estimates of the costs and risks of an actual trial are made only after a motion has been denied. Overbroad motions for summary judgment are sometimes designed to make the opponent rehearse their case before trial.