When you have finished inserting groups of bristles into the head of your broom or brush, set the brush aside to dry. When you are sure the bristle clusters are firmly in place, use sharp scissors to trim the outside row on one edge to length, then work back through the brush or broom trimming each row to match the previous one. When your brush is roughly even, turn it bristle side down to see if it will stand square. If not, trim the problem bristles to length. When the brush stands roughly square on its bristles, turn it over and give it a final neat shaving with your sharp scissors, this time cutting across all the rows at once, going over the brush in several directions to make sure everything is trimmed as close to a single length as possible. If you wnat your brush or broom to look well used, trim the outer edges slightly shorter than the center of the brush.