Plaintiff assigns as error the denial of his motion for summary judgment and the granting of summary judgment in favor of Duke Power Company. Although the trial court did not specify the basis upon which defendant’s motion was granted, our review of the record discloses two grounds upon which the trial court’s order can be supported, either of which would entitle defendant to summary judgment. Accordingly, the trial court’s judgment must be affirmed.
The rules with respect to summary judgment are well established. Summary judgment is properly granted “if the pleadings, depositions, answers to interrogatories, and admissions on file, together with the affidavits, if any, show that there is no genuine issue as to any material fact and that any party is entitled to judgment as a matter of law.” G.S. 1A-1, Rule 56(c).
An issue is genuine if it “may be maintained by substantial evidence.” (Citations omitted.)
[A] fact is material if it would constitute or would irrevocably establish any material element of a claim or defense. (Citation omitted.)
City of Thomasville v. Lease-Afex, Inc., 300 N.C. 651, 654, 268 S.E. 2d 190, 193 (1980). The moving party must establish not only the lack of a genuine issue as to a material fact, but also that he is entitled to judgment as a matter of law. Johnson v. Phoenix Mut. Life Ins. Co., 300 N.C. 247, 266 S.E. 2d 610 (1980). The evidence presented must be viewed in the light most favorable to the non-movant. Koontz v. City of Winston-Salem, 280 N.C. 513, 186 S.E. 2d 897, reh’g denied, 281 N.C. 516 (1972). Summary judgment is rarely appropriate in negligence cases, even when there is no dispute as to the facts, because the issue of whether a party acted in conformity with the reasonable person standard is ordinarily an issue to be determined by a jury. Moore v. Crumpton, 306 N.C. 618, 295 S.E. 2d 436 (1982). However, summary judgment may be granted, in a negligence case where there is no question as to the credibility of witnesses and the evidence shows either (1) a lack of any negligence on the part of the defendant, Moore v. Fieldcrest Mills, Inc., 296 N.C. 467, 251 S.E. 2d 419 (1979) or (2) *651that plaintiff was contributorily negligent as a matter of law. Brooks v. Francis, 57 N.C. App. 556, 291 S.E. 2d 889 (1982).
In this case, neither party submitted affidavits, answers to interrogatories or admissions in support of their respective motions for summary judgment. Both plaintiff and defendant relied solely upon the depositions of Mullís and Powell; there is no dispute as to the credibility of either witness.
 The first issue which we must consider is whether the evidence, considered in the light most favorable to plaintiff, raises any genuine issue as to negligence on Duke’s part, and if so, as to whether such negligence was a proximate cause of plaintiffs injury. We conclude that it does not. Although the bolt which initially broke was in the puller-tensioner when plaintiff began using the machine, there was no evidence that the bolt was other than the original bolt installed at the time the machine was manufactured, that it was improperly installed, or that Duke should have been aware, by reasonable maintenance and inspection, that it might break. In addition, there was no evidence suggesting that plaintiff was injured when the first bolt sheared. Thus, the evidence with respect to the initial incident is insufficient to raise a genuine issue as to any negligence on the part of Duke which proximately caused an injury to plaintiff.
Even so, plaintiff contends that after Duke had been informed of the initial incident, a Duke employee instructed plaintiff and Powell to use an improper bolt to get the puller-tensioner back in operation. Plaintiff argues that Duke should have known of the danger involved in the use of an improper bolt in the machine and was negligent in failing to prevent the continued use of the puller-tensioner until a proper replacement bolt could be located. The evidence, however, indicates that when Powell radioed Duke’s service center, he was told only that Duke did not stock the kind of bolt that he requested and that he would have to use whatever was available to him to repair the machine. There was no evidence that any of Duke’s employees instructed Powell or plaintiff to install an inadequate bolt in the machine or pressured plaintiff or his employer to continue the work under unsafe conditions. There was also evidence that Harrison-Wright was authorized to procure, at Duke’s expense, parts and equipment necessary to the performance of the work, and that plaintiffs foreman purchased *652several V2 inch case-hardened bolts the day after these incidents occurred. Finally, there was evidence that plaintiff fell a third time when the rope separated from the wire which was being installed, an occurrence not involving Duke. After this incident plaintiffs foreman reduced tension on the wire and the job was completed without further incident, even though plaintiff and Powell continued to use the puller-tensioner with a 3/8 inch carriage bolt installed in lieu of the proper V2 inch bolt. From our review of all the evidence, and giving plaintiff the benefit of every reasonable inference to be drawn therefrom, we find no substantial evidence of any fact which would tend to establish negligence on the part of Duke or that any act or omission on Duke’s part proximately caused any injury to plaintiff.
 Even if the evidence had disclosed a genuine issue of material fact as to the negligence of Duke, Duke would nevertheless be entitled to summary judgment on the basis of plaintiffs contributory negligence as a matter of law. The evidence establishes that plaintiff was fully aware that the mechanism connecting the motor to the reel required a casehardened V2 inch bolt because of its strength. He also knew that a V2 inch bolt had sheared, causing him to fall. Nevertheless, he proceeded to operate the machine using a weaker 3/8 inch carriage bolt. When the smaller bolt failed, plaintiff fell again and sustained an injury.
“[T]he law imposes upon a person sui juris the obligation to use ordinary care for his own protection, and the degree of such care should be commensurate with the danger to be avoided.” Mintz v. Town of Murphy, 235 N.C. 304, 314, 69 S.E. 2d 849, 858 (1952). A person is considered to be contributorily negligent if “he acts or fails to act with knowledge and appreciation, either actual or constructive, of a danger of injury. . . .” Clark v. Roberts, 263 N.C. 336, 343, 139 S.E. 2d 593, 597 (1965).
The evidence discloses that plaintiff was aware of the danger involved in operating the puller-tensioner without the proper bolt, that he proceeded to use the machine notwithstanding such knowledge, and that he was injured by reason of such conduct. Thus, his use of the machine rendered him cpntributorily negligent as a matter of law.
*653Because we hold that defendant’s motion for summary judgment was properly allowed, we deem it unnecessary to discuss the denial of plaintiffs motion for summary judgment. The judgment of the trial court is
Chief Judge HEDRICK and Judge EAGLES concur.