Shutter is a gambling term used to refer to a card or board that has bingo numbers on it. Depending on the venue you’re playing in, the shutter can come in different sizes, colours, and shapes. However, its purpose is always the same.
As the numbers are drawn from the bingo cage, players can use the shutter to mark the numbers that have been drawn. Due to the shape of the shutter and the action of marking the numbers, the whole process feels like shutters going up and down on a solitaire building, which is how the shutter earned its name.
Sometimes, venues might even use large shutters so that players can always verify the numbers drawn in case they think they have missed a number or two.