I have The Betterly straight line tool, and it's worth every dime !! It makes joining rails a breeze, and the accuracy and speed it does it at is extremely impressive compared to traditional methods.
Just out of curiosity when I first bought the tool, I checked the accuracy it delivers, and it was consistently within thousandths at the connection......with a simple turn of the two knobs and tightening the rail screws.
Where I found it the most impressive is when I was using the Parallel guides to rip down a bunch of 4x8 sheet goods, and with the constant sliding and moving of the rails, it can, and will cause the rails to become misaligned, and the straightline will suck them right back into place quickly and easily.
I use the connector daily, and i think for anyone who is looking for a easy, fast and extremely accurate method of joining rails, the tool is a must !!!
If anyone wants to see some close up pictures of the tool in action, just let me know !!
Thanks
David