a makeup pencil is made variable in length by use of rack shafts and a pinion . the pencil has three housings which interact to extend the brush when in use . the brush is projected out of one of the housings through a through - hole . the pencil structure has a flexible piece which seals the inside of the pencil over the through - hole when the pencil is not being used in order to prevent penetration of foreign materials in the air such as powder and dust into the pencil .