Are tennis players at the French Open allowed to scrape the mark where the ball landed?

The long-running series in which readers answer other readers' questions on subjects ranging from trivial flights of fancy to profound scientific concepts Watching the French Open tennis being played at Roland Garros, I saw a player scrape the clay court with his foot to indicate to the umpire where the ball had gone out on the baseline. Is this allowed? Veda Burrows, Scarborough