Contact igus and order the following parts:
(1) WS-16-60 Drylin 'W' rail 1000mm
(1) WW-16-60-10 Drylin 'W' carriage
It’s easiest to call or email your order (I always recommend you call).
1-888-803-1895
sales@igus.com
Next, run to the hardware store and get:
The 1000mm length of rail, which is about 39" long, gives you a good 36" of slide and has 9 evenly spaced holes pre-drilled in it, so all you have to do is tap the middle hole!
Tap the center hole of the rail. This is where you’ll screw the rail to the tripod.

Find the center of the carriage and drill a straight hole with the 5/16" drill bit. Tap the hole. Screw the bolt you bought into the carriage from the bottom so its threads are sticking out the top. This is where you'll attach your head (I'm using a Manfrotto 701).
That's it! Screw the rail on the tripod (I'd be sure to sandbag the legs, cause as you go way out, it could tilt over on you), put your head on the carriage, put the carriage on the rail, mount the camera & you're ready to go. It takes about 30 minutes total, including the trip to the hardware store, to complete this project.
If you’d like to add the ZazaSlider Feet or another end-stop solution, you will need to tap the ends of the rail too. If using the 16-60mm rail, the holes are already there, you just need to run the 3/8”-16 tap through each end of the rail. The ZazaSlider Feet will simply attach with the included 3/8” flathead screws!
To use the ZazaSlider Feet with the smaller rail (10-40mm) you will need to drill and tap 1/4”-20 holes in the rail end and attach with the included 1/4” flathead screws.
Another option for basic end-stop:
Here are the part numbers of the stuff you’ll need at Home Depot:
(4) Cap Screw Socket 3/8" x 1" UPC# 30699 72208
(4) Spacer 3/8" long/nylon UPC# 30699 87368
Thanks to "CineGang" for this great end-stop solution!

Get a 6mm tap & drill set and 6mm thumb screws (two in package).
When you want to lock the carriage in place, simply screw the thumb screw in until it's tight.
I recommend using a delrin screw as it is less likely to damage the drylin bearing in any way.

This is OFFICIAL igus procedure for "aligning" the carriage.
It only needs to be done once.
They say
For more information, you can read the original thread that started it all over at DVXuser:
http://www.dvxuser.com/V6/showthread.php?t=145701