Anyone who plays on the Saturday of a major competition must enter the competition on that day rather than play it on the Sunday – unless they are playing in a club match or knockout competition.
Or to put it another way, if you play golf on the Saturday but don’t enter the major competition on that day, then you can’t enter the competition on the Sunday.
This is to prevent people having a knock on the Saturday in order to gain knowledge of flag positions prior to playing on the next day.
If the course is closed on either the Saturday or Sunday of a major competition, then the competition will be postponed and replayed at a later date over a convenient weekend.
By order of the committee, members competing in major competitions must go out in three or fourballs rather than as two-balls. This is to avoid any suggestion that there might be collusion on scoring and is common practice at most golf clubs.