To use, simply remove monitors from the protective plastic packaging and place anywhere monitoring of bed bugs is needed. Suggested placements: between the mattress & box spring at each corner of the bed and along baseboards next to the bed. Monitors will provide up to 6 months of continuous monitoring once removed from protective plastic packaging. There are 4 monitors per plastic package for convenience and better inventory control as many installations are between box spring & mattress at corner of the bed. At the end of the day, there are less un-packaged monitors left to store for future installations….better inventory control and better product protection.