A single piece on a point is called a blot. When a blot is hit by the opponent, the single piece is removed to the bar. This is effectively off the board, and the piece must then re-enter before any other piece can be moved. A player with a piece on the bar must re-enter the board after throwing a number that places that piece on an unblocked point in the opponent's inner table. Example of a black prime in black's inner board.
White piece is unable to re-enter board.
An opponent's piece cannot rest on that point, but it can move past it. Example of a blot. A checker can't touch down on a blocked point. For example, if you roll 4-2 and want to move 6 with one piece but both the 4 and the 2 are blocked, that move is not allowed. An unlimited number of pieces can rest on a point.