Assuming you're talking about the Rat Zapper Classic, here are detailed instructions from the manufacturer on how to clean it:
1. Remove dead rats and batteries. To remove a dead rat, lift the black trap door located on top of the unit and pull out the tray. If necessary, use gloves when handling dead rats. If you need to replace batteries, unscrew the battery cover on the bottom of the unit using a Phillips head screwdriver.
2. Spray inside of trap with disinfectant or soapy water and let dry completely before continuing. We recommend using a disinfectant such as Clorox Multi-Surface Cleaner + Bleach3 or Lysol All-Purpose Cleaner Complete Clean with Bleach3. Be sure to follow product directions for proper dilution and ventilation while cleaning.
3. Using a small brush (toothbrush), scrub any visible dirt or residue off of all metal surfaces inside the trap including: both electrodes, metal plate around electrode area, interior sides and bottom of housing, and inside corners where walls meet floor/ceiling (pay special attention to these areas). Rinse all surfaces with clean water afterwards and let dry completely before continuing (about 10 minutes). You may also want to wipe down exterior surface of unit at this time if desired.
4. Inspect all four screws holding electrodes in place and ensure they are tight – retighten if necessary using Phillips head screwdriver (do not overtighten). Check that metal spring clips holding electrodes are in place and not damaged in any way – replace if needed (contact Rat Zapper customer service for replacement parts877-500-6286). Wipe away any visible dirt or residue on outside surface of housing including: top lid area around black trap door, bottom area around battery compartment, corners where walls meet floor/ceiling, etc., using small brush (toothbrush) if necessary – be sure no dirt or debris is blocking air vents located on backside of unit near bottom edge as this can cause overheating during operation which will shorten lifespan of electronics inside unit!5 Finally, check that red “kill grid” indicator light is still functioning properly by pressing test button located next to it – red light should illuminate briefly each time test button is pressed indicating kill grid is functioning correctly