How to make a string jig for those of us that have spent all the rest of our cash on kit...

Quite simply, get a bit of threaded rod, and cut to length. A bit of pipe with a washer top and bottom serves to provide a smooth surface so your material doesn't get caught up in the threads. A nut top and bottom holds it in place. Then another nut and washer to bolt it to the crosspieces.

Where, as you can see, we've recessed the bolt that holds the threaded rod to the crosspiece. This is why it's best to use threaded rod - you can faff with the length of the posts. A bolt would be better from the point of view of integrity, but really makes no difference if you're using beefy enough rod - 10mm is probably best, 8 is a minimum because less than that and it'll bend.

Anyway, so you have your four posts, and bolted to a pair of crosspieces. How big should all this be? Well, at a guess... The sections of rod need to be at least 6" long to let you spin the serving tool round to do the endloops. The crosspieces can be as long as you like, but around a six inch gap between the bits of rod is a minimum (fiddle factor). Then the main section...

Here we have the crosspieces bolted onto the main section. This is just a length of 3" by 1.5" timber that I found lying about. As to getting the length right - drill a hole at one end, bolt one crosspiece on. I've used another load of threaded rod (offcuts) and a butterfly nut (AKA wingnut). These are essential, because otherwise you'll be down for using a pair of pliers to tighten and loosen the crosspieces, and you'll never manage it all that well. Trust me here, I tried for a fair while. Also, make sure you don't have a washer between the main section and crosspieces, it impairs the friction that helps with holding them square. But you do need a washer either end of that bit of threaded rod to stop the nuts sinking into the wood and doing Bad Things (TM).

Anyway, having bolted one crosspiece on, align it parallel with the main section (pointing along it), and put a string on the post that's hanging off the end of the main section. Then do the same with your other crosspiece, but not bolted down, obviously. Move it so it's in the same sort of thing (pointing down the main section, and has a string on the post that's furthest away from the other crosspiece). Mark where the centre of this is on your main section, and then hack out a groove going up and down from there. About six inches either side does nicely for most stuff.

A note: For God's sake make sure your crosspieces have been drilled for the bolt that holds them to the main section in the absolute centre. Because otherwise your strings will be perenially lopsided and a bugger to make.

Cutting the groove is dead easy. Drill a big old hole at either end of your desired groove (I made this out of 12mm rod, so used a 14mm drill) and then just join them up with a convenient saw. I used a jigsaw because I'm lazy (think Home Improvement, Tim Allen's Tool Time, MORE POWER!, *grunt grunt grunt* ) and then just bolt it all together.

Enjoy!