KitsJAG5254

Sup guys.. here is the deal. I have a water temperature gauge on the pillar and have the light working except for the sensor part (the needle to move/work when starting the car). I didn't connect the sensor wire yet to the thermostat because I don't have the special tool that I need. I forgot the name of it and I need to know so I can go ahead and connect them. I am looking for a tool... it's like a coupling tool that combines my sensor wire from the gauge with the wire from the thermostat. I just can't splice these wires and connect them because it'll mess it up which could tell me that the car is over heating when it is not. So if you guys know what's that little tool I need PLEASE let me know. Thanks a bunch.