Rule 21 allows for a judge to make determinations of law before trial that will eliminate cases where there is no claim or defence known to law. The Rule is applicable only where the law is clear and, in general, no evidence is allowed. It must be plain and obvious the claim or defence cannot succeed: Miguna v. Toronto Police Services Board, 2008 ONCA 799. The facts as pleaded are assumed to be true unless they are clearly absurd: Progressive v Saygili (1999), 46 O.R. (3d) 10. The Rule provides, in part:
21.01 (1) A party may move before a judge,
(a) for the determination, before trial, of a question of law raised by a pleading in an action where the determination of the question may dispose of all or part of the action, substantially shorten the trial or result in a substantial saving of costs; or
and the judge may make an order or grant judgment accordingly. R.R.O. 1990, Reg. 194, r. 21.01
(2) No evidence is admissible on a motion,
(a) under clause (1) (a), except with leave of a judge or on consent of the parties;
In recent years Rule 21 motions have been increasing brought at trial. As is obvious this is not what the Rule was intended for. That has led to some problems as can be seen in the recent decision of Holgate v. Sheehan Estate, 2015 ONCA 717:
 In this case, the trial judge's initiative in inviting a mid-trial r. 21 motion was clearly designed to narrow the issues and streamline the trial. These objectives are commendable. Unfortunately, however, the initiative produced the opposite result. The mid-trial motion resulted in a bifurcated trial, created the possibility for two appeals to this court arising from the same proceeding, and caused the completion of the trial to be delayed pending the outcome of this appeal.
 There is an additional concern. A r. 21 motion concerning a question of law is based on the pleadings. Evidence is not admissible except on consent or with leave of the court. When a r. 21 motion is conducted by a trial judge after the evidentiary phase of the trial has commenced, there is a risk that incomplete or untested evidence can inadvertently seep – or be seen to seep – into the consideration of the motion on its merits. While I am satisfied that this did not occur in this case, the danger is nonetheless real.
Based on these concerns it seems prudent not to proceed with Rule 21 motions during trial.