a rodent trap covered base defines an enclosed interior accessible through a sliding plastic tunnel defining a passageway for rodents into the interior . the tunnel has a projecting strike member , and is biased by an underlying spring to a retracted position . a trigger engaging member extends from the tunnel to be retained by a catch on a trigger mounted to the base . when a rodent passes through the tunnel into the base interior , it is directed by barriers towards a rodent attracting bait . to reach the bait , the rodent must press against a pivotably mounted trigger , thereby dislodging the trigger from the trigger engaging member which releases the tunnel to be driven by the spring to retract along parallel tracks to bring the strike plate forcibly against the rodent within the trap , usually killing it , and closing the trap , which is then presented covered within the trap for disposal .