When speaking with PMPs it surprises me how many are unaware of what the F&S stamped on the yellow expanded trigger of a Victor mouse and rat snap trap actually stands for. It does not stand for fast and slow which many believe. The F&S actually signifies Firm and Sensitive which is just the opposite of what many believe. The expanded trigger allows you to easily adjust the sensitivity based on where you place the locking bar when setting the trap. When placing on the S or sensitive setting it will fire with the slightest touch or vibration which is likely too sensitive. When setting on the F or Firm side it will take more effort to fire the trap. The firm setting would be used in areas where vibration may be an issue such as a warehouse with tow motor activity. Most times for best results I suggest just setting the trap in the middle. By knowing this basic piece of information for a key tool used every day it will allow you to be more successful while performing your rodent control services. It may also prevent you from getting your fingers snapped!