This is a sweet garage sale find. As Wormil explained, the yellow is the main body of the “clamp and drill” jig – you clamp your workpiece against the plastic backer block with bushings, and drill through the bushing guides to bore an angled hole in your workpiece. The two plastic parts on either side of that are gauges for the bit stop/collar – these gauges were made part of the base unit on the newer Kreg jig, so if you end up with a manual for a newer jig don’t let that throw you off.
I was going to post a guide on how to use a Kreg jig, but it is surprisingly hard to describe in text. Literally one or two youtube videos would be worth 500 words. This may be a good start: http://www.youtube.com/watch?v=1XQFDncTavE.
-- Dan in Minneapolis, woodworking since 11/11.
