Actually that's Brian Sedgeley trainer at Festool USA. And that is the method they teach at the training classes.

Seth

So, what is being done?  Tried to view video, but couldn't because I'm not on facebook, and I'm not about to join.

@Bohdan

Thanks!  Didn't occur to me to select "not now" - duh, guess I need my morning coffee.  Again, thanks.

A year or two ago, this particular method was thoroughly discussed on the FOG, and like everything else, some liked, some did not - so, as I keep saying ... everyone's mileage may differ.  I do find that one will/should use whatever works to gain the success desired.  Good to see this again.

While I tried using the TS method, I find it quicker to use a straight edge at hand for the alignment.

The TS method has the downside of a connector in the bottom slot not being accessible as the rails sits on a surface with the saw ontop, having to flip the rails over to tighten the bottom connector gives great potential of misalignment - as did using only one connector (at least with the Festool ones).

Thus, having to join rails to cut big sheet goods I:
1) sacrificing some mm of material for the cause to make me a straight edge (one cut with a single rail) from one sheet
2) join the rails with the connectors, only tightening one screw a little each to stop the connector from sliding out
3) flip the rails over and with the rail cutline in the middle of the fresh straight edge just created push the 'rail' part (that the TS use as its reference) against it, resting the flat part of the rails ontop the sheet
4) tighten the connectors - easy in that position as both are fully accessible since the upper slot of the rail (facing downward while aligning this way) is outside of the board and reachable

Way quicker in my view and less prone to misalignment...

Don't join rails much, but I have used both a straight edge and the method in the video (after taking a Festool class). Both work equally as well, regardless of other posts in this thread. There is some logic in it since your saw is what is riding on the rails and, if your saw, is set up to run true on the rail, then it should line the rails up when joining them. I agree, though, it really isn't faster than using a straight edge and both do get the same result, both in class and in my shop.

I want to add a comment /question but I am not in front of my rails now and won't be for a few days. I will ask it here so I don't forget my thought (this happens to us old guys). What if you took a 2-3 foot long piece of stable material, MDS, aluminum or some firm hard plastic and milled a dado the exact size of the main channel. You could fit it tightly to the channel and both pieces would be in alignment. If you added 2-3 set screws on each side you could snug the channel up tight to one side and then it would be pretty accurate. I am just thinking here and I can't look at my rail to see if there is some reason this would not work. Just trying to contribute an idea if anyone can make it better jump in. With all the great tinkers on this forum we should be able to develop a low cost, dead on accurate way to do this important task.

Before I got a long rail, I joined together two rails for many, many cuts, hundreds' likely using nothing more than a square, if anything. If your rails are not cut straight enough for your liking, file the crooked one so it is straight. Mine were virtually 100 square from day one so took nothing to line them straight. I wouldn't waste my money on some gimmick.   
BW

Quote from: grbmds on April 18, 2017, 02:05 PM

if your saw, is set up to run true on the rail, then it should line the rails up when joining them.

No, when the saw rides on the rail both contact points (green gibs) are engaged, hence it stays true. When one gib is off the rail the saw may not run true.

They aren't both off. Anyway, not important. It works and that's really all that counts. Right?