NOT much to them, just two pieces of relatively light guage sheet metal (2" long and 3/4-1" wide) with a hole in each end for the bolts. I used a piece of galvanized steel from one of my house window shutters I took down. It is 1" wide and about 1/16" thick.
Run the factory bolt thru one end of the 2'' "extender" and screw it into the original factory crossmember mount. Then take another small bolt and nut and bolt the factory hand brake line mount to the other end. This "pushes" the line forward a little and takes some of the the "U" shape out of the line.
If you lay on your back under your truck and look straight up at the hand brake lines where they bolt to the frame cross member, you'll notice the hand break cable is kind of "U" shaped (to the rear). The point where the lines are secured to the crossmember appears to be FARTHER back than where the cable goes through the little rubber guide bushings (by the rear wheels). The two inch tab kind of "pushes" the cable back forward and takes most of the the "U" bend out of the line.
When I put the coil spacers in, and later on another truck the OME springs, I had to unbolt the two hand brake lines from the cross member in order to get the axle to tip enough for the springs to fall out and to reinstall. This "extender" doesn't make the hand brake lines longer, I think it just allows you to use more of the stock hand brake line from the crossmember. You still want to make sure the insulator on the hand brake line on each side is riding within the little rubber guide next to each wheel. Not a hi-tech solution, but it keeps the lines out of harms way in about the same way the factory did. Best of all, this mod doesn't cost hardly anything, just your time really.
If you're running 3" of lift or more on the rear, I suppose... you should consider a new/longer replacement lines. You can only get so much adjustment out of the stock ones.