This case was heretofore before this court. Making our opinion therein, reported in 187 Fed. 803, the basis of the present, we avoid repetition. Upon the entering of judgment for the plaintiff by the lower court in accordance with the mandate in that case, defendants sued out this writ of error.

[1] The questions now involved, as stated in defendants’ brief, are: First:

“On the trial of an action of assumpsit on a building contract, the plaintiff is permitted to file a supplemental affidavit of claim, alleging that the contract was completed. In reply thereto the defendants are permitted to file a supplemental affidavit of defense, denying the completion. May defendants prove noncompletion, and the consequent damage, without giving 15 days’ notice as required by rule of court?”

And second:

“Variance between contract sued on and contract proven.”

In regard to the first question the lower court said:

“The court being of opinion that the rule requires notice to be given that matters of counterclaim set up in an affidavit of defense are intended to be insisted upon, and that such notice should appear of record in the cause, and no notice having been given within the time fixed by the rule of court that the counterclaim would be insisted upon at the trial, the plaintiff had a right to presume that the matters of counterclaim would not be insisted upon. And the objection is sustained and bill sealed.”

It has always been held that a court is the best judge of its own rules, and an appellate court will not reverse such construction, except where manifestly erroneous (American Co. v. Annex Co., 226 Pa. 461, 75 Atl. 669); for, as said in Duncan v. United States, 32 U. S. 450, 8 L. Ed. 739:

“IIow can the practice of the court be better known or established than by its own solemn adjudication on the subject?”

Far from there being any gross error in the court’s construction of 'the rule, we may say its construction'commends itself to us.

[2] As to the second question, it seems that .no question was raised by the pleadings as to the correctness of the copy filed by the plaintiff with its statement of the contract sued on. During the trial the defendants, in a supplemental affidavit then filed, denied such copy was correct. The alleged variation was slight, and did not affect the merits. Subsequently, on cross-examination of one of the plaintiff’s witnesses, the defendants exhibited to him an alleged copy and proved its accuracy. Thereupon the plaintiff offered *405the defendants’ copy in evidence. This was not objected to, and the trial proceeded on defendants’ copy. At the conclusion of the testimony, however, the defendants then sought to raise the question of variance by a point in which they asked for binding instructions in their favor on the ground of variance “between the contract sued on and the contract proven by the evidence.” In view of the facts stated, the court was in no error in refusing the point, for the course of the trial had been such as to waive such objection.

The judgment below is affirmed.