Thousands of Yale students and hundreds of faculty members will join picket lines and hold pro-settlement rallies in lieu of attending and leading classes as a three-day moratorium on the use of university facilities gets under way today.

Students organized the boycott of classes last week to express their desire for a settlement of the six-week old strike by workers including Yale's clerical, technical and food services employees.

But participation in the moratorium, by some estimates limited to one-fifth of professors and half of students there, has disappointed union supporters.

About 3000 Yale employees have been off the job since the university and AFL-CIO Local 34 failed to reach an agreement on worker demands for pay raises and an end to alleged salary discrimination.

The administration has resisted pressure from students and faculty to either compromise with the strikers or submit the dispute to binding arbitration. Niether side would comment on the negotiations which began Monday.

Last week college officials sent letters to professors and teaching fellows reminding them of their obligation to fulfill their "commitment to education."

University spokesman Steve Kezerian added yesterday that any faculty members cancelling classes might be subject to disciplinary action from the college dean and from their department chairmen. The administration has also notified chairmen that members of their departments will be expected to refrain from participating in the boycott.

But Yale Corporation Secretary John A. Wilkinson said yesterday that professors, participating in the moratorium would not be seen as failing to meet teaching obligations as long as they rescheduled their lectures for later in the semester.

Biology professor John P. Trinkaus, who will be picketing instead of lecturing tomorrow, called the administration's letters threatening and hypocritical.

"It's a crime to cut a class to end a strike but not for any other reason," said Trinkaus. Professors frequently cancel lectures to travel or to speak at other universities, he explained.

He said the university had probably succeeded in intimidating many junior faculty members, but that he doubted Yale would act against professors who participate in the boycott.

Several students contacted yesterday preferred the union's position to Yale's, but some questioned the effectiveness of the boycott, saying it deprived them of a chance to learn without convincing the administration of anything.

The moratorium is the first of its kind since the protests over the 1970 Black Panther trials in New Haven.