After the first arrests (over 700 of them), students called a general strike. Classroom and administrative buildings and Butler Library had picket lines in front of them and most people honored them. Speaking for myself, the picket lines I was on (including Lewisohn and at Butler) did not repel would-be crossers physically, but rather reasoned with them in a non-confrontational way, and wound up convincing some to respect the strike or even join it. If there were physical confrontations at other buildings I'm not aware of them. In any case, students were given P (Pass) or F (Fail) grades on all their classes. Many professors passed everybody, but some required their classes to be completed to earn a P.