When installing your dimmer remember electricity flows into it on one side and out on the other side. If the dimmer has a separate wall plate tighten the.

Light Switch Has 2 Hot Wires
Installing a dimmer switch with 2 black wires. My problem is lutron says to cap off the red wire with the white stripe. Coming out of the switch itself is 2 red wires a black wire and a ground wire. If your dimmer has two black wires the orientation doesnt matter. Unlike installing a light fixture both wires going to the dimmer will be black and usually can be placed on either gold screw. As always green denotes the ground or copper wire. Fold the wires neatly into the box.
However on my switch the 2 red wires are solid. Notice the black wire is the only wire that we are controlling through the 2 way switch. If you are installing a dimmer that has a removable knob remove the knob from the dimmer by gently pulling outward. Finish the job by installing the cover plate and turning on the power to test the new dimmer. It doesnt matter if you reverse the two switch wires to a single pole dimmer. Since this is only single pole and not 3 way i dont need one of the red wires so i should cap it off.
Carefully tuck the wires back into the electrical outlet box. Tighten the screws holding the dimmer to the electrical box. You have an incoming hot wire black going to one screw it does not matter if you use the brass or silver screw on the side of the 2 way switch and a black wire from the other screw on the 2 way switch going to the load light ceiling fan etc. If there are different color combinations attach red or black to the black wire in the wall or whichever wire is hot has power. Screw the dimmer to the box with the screws provided. No stripes of any color on them.