Horses are for courses - or is it courses are for horses? Whatever the old race-track saying, the horse, Free Movement, and the course, Casanova, have an affinity for each other.

Randy Rouse's impeecably bred dark brown gelding won the 20th renewal of the Casanova Cup here today before a record crowd of close to 7,000 - the classy jumper's fifth victory in this 2 1/2-mile timber steeplechase.

Free Movement won the Cup in 1972 and 1973, was out of training during 1974, returned to win it in 1975 and again last year. His margin today was three lengths over Roy (Tennessee) Graham's Boca Bird with Bill Myers, on Frost Time, another six lengths off.

"He's amazing," said Rouse - who is amazing in his own right, standing today in the Casanova winner's circle for the eighth time in the past 11 years, "I didn't intend to use him today . . . we hunted for four hours Wednesday . . . then it came up soft and he loves that."

The Casanova course was soft, "deep at the fences," according to one race veteran, and Free Movement ate it up. He ran his usual race, letting another horse - this time Boca Bird - set the pace over 18 of the 19 fences. Coming up the hill going into final jump Rouse gave the Independent gelding the sign and they went on top on landing.

Boca Bird, as usual, refused to quit and drove under wire six lengths to the good of Frost Time, whom many in the crowd had expected to use its speed down the stretch.

Casanova's eight-race card had all the form of a midseason meet with Virginia's top woman rider. Patty Cassell and the horse that carried her to that title in 1976, Never Delay, paring up for the first time this year to win the Melrose Castle by five lengths over D. J. Nahar. Top gentleman rider of last year, Arch Kingsley, was out of the money in both the Cup and the First Colony Life Trophy race.

The latter was won by Randy Waterman - riding with a broken wrist and a separated shoulder - on Joananns Brother by five lengths over last year's First Colony champion, Kevin Palmer's Kool Kake. Chick Owens, a winner last week at Fairfax with High Peak, was third in this owner-rider hurdle series.