are these one time use? or can they be cleaned and used multiple times?

Most contractors clean them and use them a few times. If you are rough with stencils in general, it is possible they would crack on the first go but in general that hasn't been our experience. If you're looking for something with more reusability, we can...

36" x 16" Number Kit Stencil 12-pc Kit

Professional-looking, clean, crisp markings, directions, and signs on parking lots, roads, curbs, and driveways can be easily attained with the aid of stencils. Made from high-quality LDPE, the 36" x 16" Number Kit Stencil 12 pc. Kit offers an effortless solution to an otherwise difficult and time-consuming job. This stencil kit includes 12 pieces from 0 through 9 with two blank stencils. Overall size per stencil is 42" x 20". Not only aimed for property owners and line striping professionals, our stencils are also ideal for do-it-yourselfers and homeowners. Reusable flexible LDPE material effortlessly lays flat on pavement, wood, glass, hard plastic, and other non-porous surfaces. Available in three varying thicknesses - 1/16" (.060"), 1/10" (.100"), and 1/8" (.125") - simply flex stencils to remove dried paint, and then roll up for easy storage.