This is an appeal from a judgment in a negligence action for the defendant. We affirm.
On December 27, 1972, during the course of his duties, Frank Watson, an employee of Union Carbide Corporation, was injured in a 35 foot fall when a steel bin above him came loose. At the time of the accident Calvin McGee, a contractor, was performing demolition work at the plant pursuant to a contract. Part of McGee’s job was to dismantle one of the furnaces. As a final step in the dismantlement, a steel bin had to be removed. The accident occurred when the bin was cut loose by a member of McGee’s crew. After the accident Union Carbide conducted an investigation and obtained statements of several witnesses, including James Tolbert, a member of McGee’s crew, who died prior to the trial.
Watson, the injured employee, filed suit in the Circuit Court of Colbert County against the contractor, McGee, seeking damages of $500,000 for negligent and/or wanton injury. Watson relied on the safety provisions in the contract while McGee claimed Watson was contributorily negligent. The jury found for McGee and Watson appeals.
I.
It was not reversible error for the Circuit Court to admit into evidence the written statements of Tolbert who died before the trial and who never testified. The statements were in the form of two exhibits, numbered 4 and 2A.
Exhibit 4 was entered into evidence by stipulation of the parties. This exhibit was attached to a pre-trial order which, under Rule 16 of the Alabama Rules of Civil Procedure, controls the subsequent course of the action. Moreover, the objecting attorney admitted several times at trial that the parties had agreed that Tolbert’s statement would be put into evidence. Agreements and stipulations made in a pretrial order and admitted in court are binding on the parties and admissible into evidence. See Prestwood v. Watson, 111 Ala. 604, 20 So. 600 (1895); Brunswick v. Regent, 463 F.2d 1205 (5th Cir. 1972).
Exhibit 2A was an excerpt from an accident investigation report. It was a summary of a statement by Tolbert taken by the Superintendent of Industrial Relations at Union Carbide. As admitted by the objecting attorney at trial, there is no significant difference between the two statements, as contained in Exhibits 4 and 2A, except the inclusion of the name “Hovater” in Exhibit 4. The appellant must not only establish error but also must show that he was probably prejudiced by the error. Shelby County v. Baker, 269 Ala. 111, 110 So.2d 896 (1959). Since the statements are substantively the same and since Exhibit 4 was properly admitted into evidence, there was no prejudicial error as to Watson.
II.
It was not reversible error for the lower court to admit into evidence the parol testimony of Robert Downie, Assistant Superintendent of Engineering and Maintenance at Union Carbide, concerning the contract between Union Carbide and McGee.
*464Watson first objects to the trial court’s allowing Downie to testify that it was his understanding with McGee that if McGee had any problems or questions about the job, he was to consult Downie. There is no prejudicial error here. None of the parties to the contract is attempting to vary the terms of the contract by this testimony. In fact, the parties to the contract agree as to their understanding of the contract. It is a non-party who is complaining.
Next Watson complains that the trial court erred in allowing Downie to explain § 25 of the contract. A contract may be explained consistently with its terms. Chastain & Blass Real Estate & Ins., Inc. v. Davis, 280 Ala. 489, 195 So.2d 782 (1967). In order for the court, to properly interpret the contract, the court may use parol evidence to put itself in the position of the parties. American Mut. Liab. Ins. Co. v. Tuscaloosa Veneer Co., 237 Ala. 187, 186 So. 133 (1939). There was no attempt to challenge the contract or the meaning of its terms. Downie was merely asked to illuminate its meaning. Parol evidence is admissible to explain the writing or to show the purpose and character of the transaction. 30 Am.Jur.2d Evidence § 1065 (1967) (citing Baker v. Gregory, 28 Ala. 544 (1856)). Since this evidence aided in the interpretation of the writing by placing the court in the position of the parties, it is admissible.
Watson also questions the lower court’s allowing Downie to testify that he instructed McGee to remove the catwalk on the ground that such an instruction would be an oral modification or contradiction of a written contract. Parties to a written contract may by mutual consent without other consideration orally alter, modify or rescind the contract. Allied Mills, Inc. v. St. John, 275 Ala. 69, 152 So.2d 133 (1963). Downie’s testimony was thus admissible.
III.
The trial court did not commit reversible error by sustaining an objection to a question asked by Watson on cross-examination of McGee’s witness. The question was as follows:
“Let me ask you on page 9 of Plaintiff’s Exhibit No. 6, it says ‘when working overhead, station a man below or use danger signs and rope off to warn others of the danger.’ Would you say that rule should have applied to Calvin McGee and the work he was doing?”
The refusal to allow a witness to answer a question calling for a conclusion of the witness and invading the province of the jury was not error. Jackson Lumber Co. v. Butler, 244 Ala. 348, 13 So.2d 294 (1943); O’Rear v. Richardson, 17 Ala.App. 87, 81 So. 865 (1919). See 98 C.J.S. Witnesses § 328 (1957).
Asking a witness whether something should have applied is asking the witness to give his opinion about something not within his knowledge. Even if he could have drawn a conclusion or offered a guess, such a response would be of little value in a proceeding supposedly based on fact and law, not mere opinion.
On direct examination, the witness was asked what safety rules were in effect at the site at the time of the accident, whereas on cross-examination he was asked whether a specific rule should have applied. The answer to Watson’s question could neither explain nor rebut any prior issue. Sustaining this objection did not deny Watson’s right to respond in kind or his right to a searching and sifting cross-examination.
“Opinions should never be substituted for obtainable facts.” Dersis v. Dersis, 210 Ala. 308, 98 So. 27 (1923). Since the contract in question was in evidence, the question of what safety rules were applicable was a question for the jury. Therefore, the objection to Watson’s question was correctly sustained.
IV.
It was not reversible error for the court to allow McGee to answer questions concerning instructions given him by Downie.
Watson at lower court specifically objected to a question asking if Downie told McGee that he would keep the Union Car*465bide people out of the demolition work area. However, the court sustained the objection and no answer was given; thus, there was no prejudicial error. Madison Highlands Dev. Co. v. Hall, 283 Ala. 333, 216 So.2d 724 (1968).
Watson also objected to the question, “And did you [McGee] put it [the rope] up at the request of Mr. Downie?” Although the objection was overruled, there was no prejudicial error because the matter of Downie’s request was thoroughly covered in both prior and subsequent questions which were not objected to. See Central of Ga. Ry. Co. v. Lee, 227 Ala. 661, 151 So. 840 (1934); Prosch v. Prosch, 47 Ala.App. 33, 249 So.2d 855 (1971).
We will not consider whether certain questions now complained of were inadmissible because they elicited hearsay responses, because these questions were not objected to below by Watson. An objection must be made to a question and a ground stated therefor, or the objection and any error is waived. Madison Highlands Dev. Co., supra; 88 C.J.S. Trial § 115 (1955). Therefore, if no objection is made, there is no error in allowing into evidence the answer.
In view of the above, and in light of the fact that Downie’s testimony verified McGee’s answers, and that both Downie and McGee were available for cross-examination, we find no prejudicial error in the court’s allowing McGee’s answers into evidence.
AFFIRMED.
TORBERT, C. J., and BLOODWORTH, EMBRY, and BEATTY, JJ., concur.
MADDOX, J., concurs in result.
JONES and SHORES, JJ., dissent.
ALMON, J., not sitting.