"Strictly speaking, custom is that length of usage which has become law. It is a usage which has acquired the force of law."29 The words "custom" and "usage" are often used as convertible terms.30
"A custom or usage which binds the parties to a contract does so only upon the principle either that they have knowledge of its existence or that it is so general that they must be supposed to have contracted with reference to it."31 Where a usage is local, its existence must be clearly proved to have been known to the party sought to be charged thereby, at the time.32 Not only the existence of a usage, but whether knowledge of it exists in any particular case is a question of fact for the jury.33 Evidence of usage is received as is any other parol evidence, when a written contract is under consideration.34 Some cases hold that the custom may be proved without being pleaded.35
26 Citing 29 Am. & Eng. Enc. Law (2d Ed.), 423, et seq.
27 Brady v. American Mach. Co.. 80 App. Div. 269 (N. Y. 1903).
28 Hedenberg v. Seeberger. 140 111. App. 618 (1908).
29 Walls v. Bailey, 49 N. Y. 471 (1872).
30 Id., 472.
31 Harris v. Tumbridge, 83 N. Y. 92, 100 (1880).
Where there is an express contract as to the amount of compensation, and the contract is not vague or uncertain, it cannot be altered or affected by any proof of usage, and proof of custom in such a case is therefore inadmissible.36 In other words, where the contract covers the point involved, proof of custom as to such point is not proper.37
It has been said that where a person brings about a sale and attempts to recover commissions at the rate usually charged by brokers, he must show that he himself is a broker.38 In another case,39 it was said that "in an action for reasonable compensation by one employed to sell real estate, and who effects a sale, but who is not regularly engaged in that business, evidence of the customary charges of real estate agents for such services is relevant; but such customary charges are not conclusive in fixing the compensation of the person making such sale in such circumstances."40
Again, in the same case 41 it was held that, "The right of one rendering services for another to have their value estimated under a quantum meruit upon a basis of commissions can only arise out of a general custom, so that, where such custom exists in reference to certain kinds of business, any one actually or presumptively having knowledge of it, and employing the persons engaged in such business to perform services in their line without special contract, will be presumed to have done so with reference to such custom; but this rule only obtains where the persons employed are regularly engaged in the business to be transacted.42 Plaintiff was not engaged in the real estate business, so it cannot be assumed that defendants ' promise to recompense her for the services she rendered was made with reference to, or upon the basis of, commissions usually charged by real estate brokers. In such circumstances she would only be entitled to recover what her services might reasonably be worth independent of the question of the usual commissions charged by brokers, although evidence of the customary commissions charged by real estate agents would be relevant to consider in fixing the value of her services."
32 Hlggins v. Moore, 34 N. Y. 425 (1866). 33Walls v. Bailey, 49 N. Y. 476 (1872). 34 Id., 470.
35 Sleidtmann v. Lay Co.. 234 111. 89 (1908). As to pleading custom, see Poland v. Hollander. 62 Misc. 523 (N. Y. 1909).
36 Main v. Eagle. 1 E. D. Smith 619 (N. Y. 1852) ; Goldstein v. D'Arcy, 201 Mass. 312 (1909).
37 Emery v. Atlanta Exch.. 88 Ga. 326. 330 (1891), (citing Glbney v. Cnrtis, 61 Md. 192; Corbett v. Underwood, 83 111. 324; Werner v. Footman, 54 Ga. 128).
38 Main v. Eagle. 1 E. D. Smith 619 (N. Y. 1852).
39 Fleming v. Wells, 101 Pac. 66 (Oolo. 1909).
40 Citing Kennerlv v. Sommervllle. 61 Mo. App. 75; Erben v. Lorillard, 41 N. Y. 567; 3 Sutherland on Damages (3rd Ed.), 451.
41Fleming v. Wells, 101 Pac. 66 (Colo. 1909).