One flow-trap design is the box-nramp trap. The box-n-ramp trap consists of an impervious box (e.g., plastic trash can or metal drum) into which water is pumped and a ramp which carries the out-flow water to the pond bottom (Figure 7). The crayfish move up the ramp against the flow and are trapped when they fall into the box. Adding fiberglass screen, vexar, or some other rough texture to the surface of the ramp will help the crayfish climb into the trap. Flow-traps must be checked often (every few hours) as they can fill with crayfish, causing those in the bottom of the trap to suffocate.