KitsJAG5254

Ok.. I have installed my volt gauge and my tach.. and some of you guys probably have seen them.. anyways.. i have one problem.. I have the volt and tach working except my water temp gauge.. I left the sensor wire from the water temp gauge in the engine bay (somewhere safe).. my question is does anyone here know the special tool I need to splice the wire correctly and connect it to the wires of the thermostat? I think there's a tool to connect these wires really good without damaging the sensor or anything.. don't know what's it called and i'm having a hard time finding it.. help help.. thanks guys..