I got this from another forum:
This table is 16x3 and about 4 feet off the ground.
20 feet of plastic coated wire (rolls easier and won't rust)
1 set of close line tensioners
4 feet of chain
brass snaps (1)
2 "quick links" (to fasten snaps to chain and pulley)
2 sheets of 1/2' plywood (1/4" would do)
9/16 X 6" galvanized stove bolts w/washers and lock nuts (22)
Box of 2 1/2" sheet rock screws
1 26x1" wide leather collar (if training labs, a 22"or24" collar would be fine for pointers and continental breeds)
I would "invest" in pressure treated lumber for the 4x4's and 2x4's as well as marine grade plywood. I personally would stay away from pressure treat on the 2x6's as this is the portion the dog is going to be in contact with and the arsenic they use in some of that pressure treat has been reported to cause illness in kids, so I believe it is no longer legal to use that in playground equipment.
layout the 6 2x6's and using one of the 1x6's cut into 3 foot strips place cross members every 4 feet to create your table top (work area). Affix the decking to the 2x6's with the sheet rock screws.
Run a 1x6 frame around the table.
cut 3 of the 4x4's into 6 4-foot legs and affix to the top you just completed, one at each corner and two in the middle. Use the stove bolts to attach all 4x4's (I used 3 per, 2 per might be enough)
run a 2x4 frame around the legs about 2 feet off the ground. Cut the plywood to length and screw to the top of the 2x4's. This provides stability and a shelf to store gear on. You obviously can omit the shelf, but I've found the small added expense is worth the return you get in functionality, especially if this is in the garage or barn.
Affix the other 2 4x4's at each end. Level them with the ground to add 2 more legs. These are your poles for the over head guide wire.
Affix your tensioners and wire, putting the pulley on the line first. The coated wire is great because it resists rust and allows for the pully to pull easier and quieter. The 4 foot chain is coupled to the pulley on one end and the snap on the other using quick links. This way you can adjust the length for each dog quickly and easily.
Use 3 screws to affix the leather collar to one of the posts.
That should do it, if you find any problems let me know, but it should go together in about an hour. You can easily modify this design down to 12 feet or even 8 (much less than 8 feet and I think you are seriously limiting yourself).