I have a jig, but did not use it on my last build. It however would be just a bit small for the 1000 series. It would acept the 400 series, but seemed more trouble than it would be worth and I built my last few builds in the same way as Guillow describes.
The tools I use for near perfect rib alignment is magnets and I always have a small square to check my work in progress.
example of magnets on my 1000 series build.
I forget where I got it, but it would be too small for the 1000 series.
Another tool I recommend to everyone is to use pin clamps. Shorty's Basement has them. You get 28 for $3.50. I bought 2 packs. They slide over a 1 inch T pin. They have enough grip to stay where you put them when you slide it down the T pin. They last forever.
example of using 'pin clamps'... you just get the little black 'clamp', you provide the 1 inch T pin. They do not fit over a 1-1/2 inch T pin.
So that's how I build near perfect frames and all parts assembled without a single pin hole.
Mitch