Place the Z-bar with the flat side on top of the solid flooring. Face the side with the teeth toward the carpet.
Attach the Z-bar to the floor by installing screws in the screw holes on the side with the teeth.
Trim the carpet padding to the edge of the Z-bar on the carpet side, using a sharp utility knife.
Trim the carpet so it extends 3 inches past the Z-bar.
Fold the carpet back toward the carpeted room, with the edge of the fold just past the edge of the Z-bar threshold, on the carpeted side.
Place a 3-inch-wide mason's chisel into the fold at the center of the Z-bar.
Strike the end of the chisel with a hammer to push the carpet fold into the Z-bar under the threshold. Continue to the left and right of the original strike until the carpet is installed under the Z-bar.
Trim the upside-down carpet edge that is sticking out from under the Z-bar along the edge of the Z-bar. Be careful not to cut the right-side-up carpet that is installed under the Z-bar.
Strike the Z-bar on the carpeted side to bend it slightly down on the carpet. This secures the carpet to the tackless strip that's incorporated into the Z-bar.