Linear actuators are actuators which create motion in a straight line. Unlike a motor, which creates circular motion, a linear actuator can be used with any application that requires moving something in a straight line (e.g. up and down or side to side). Windy Nation LIN-ACT1 Series Linear Actuators are powerful and reliable linear actuators for small to medium loads. We designed our linear actuators with pre-lubricated metal gears, pre-installed limit switches, and with an IP65 (suitable for outdoor use) water resistance rating. Included with your purchase are two linear actuators, an up/down switch, which is used to the control the motion of the linear actuators. There are two options for the switch: Momentary and Maintained. A momentary switch will only supply power to the actuator when the button is actively engaged by your finger. When you release the button, power is cut to the actuator and it stops. The maintained switch will continued to supply power to the actuator until it is manually turned off by the end user (A light bulb switch is a maintained switch, which means it will stay on until you turn it off).