A Bat Brick is a brick cut across the width, shortening the length of the brick. A brick cut to 3/4 the length is a 3/4-bat; similarly, a brick cut in half is a half-bat. A Bat Closer is used at the end of the brick course to end the row but still make a flat surface. Brick courses are typically laid offset from the one below, which forms a stronger bond than if the mortar joints simply ran in long rows and columns across an entire wall. If you only used whole bricks in offset courses, the corner of your house would have bricks jutting from the side in every other course. A bat closer is used to finish a course and make it flush with the one below it.
A half bat closer is used on the left side of the surface shown, at every other course.
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