How do I Convert a 6 Inch Recessed Canned Light to a 4 Inch?

Turn off the breaker to the light(s) you want to change. Take out the light bulb. Remove all the trim, and disconnect the wires--red, if necessary, white, black and ground. Pull out the can section of the unit. Put an orange plastic marette on the red, black and white wires.

Make the opening 12 inches wide by 16 inches long using the sheetrock saw. Make the hole so that half of the floor joist on each side of the length is visible. Cut a piece of sheet rock 12 inches by 16 inches. Cut two 8-inch pieces of the finger-jointed pine. Place the length of the pine halfway onto the topside of the sheetrock in the ceiling cavity and screw it in place so the screws make a dimple in the sheetrock. Do the same on the other side of the cavity. Put the newly cut 12-by-16-inch piece in place. Screw in all four sides.

Cover the joints with the meshed sheetrock tape. One side of the tape is sticky. Fill up your 8-inch trowel with joint compound and use the 4-inch trowel to spread the compound evenly over the tape. Make this coat fairly thin by applying pressure. Allow recommended drying time. Continue repeating these steps for each light that you are changing.

Sand the areas--without ripping into the paper of the sheetrock--using 120-grit sandpaper. Fill up your 8-inch trowel and with the 4-inch trowel spread more compound over the joints. Make the joints wider using the 8-inch trowel. Allow the appropriate time to time to dry.

Sand the patch until smooth. Fill in the the little air bubbles that appear with joint compound and sand again. Paint the patch(es) with primer.

Mark the hole using template provided by the manufacturer. Cut the hole using the sheetrock saw. Pull the wires through remove the marettes and rewire the new light. Push the can part back into the ceiling and lock into place. Replace the trim and put in a new light. Turn the power back on.