As a knitter and a crocheter, one of the things that always has annoyed me is that there wasn't a method I'd ever seen of seamlessly grafting crochet in the way you can knitting with the kitchener stitch. I was absolutely sure it was just a matter of looking at it logically, breaking the stitch apart and working it out but I never quite got around to it. I knew though that there would need to be a different technique for each stitch.
So why graft rather than seam? Because a graft replicates the stitches and gives a smooth almost invisible join that flexes and moves in much the same way as the rest of the fabric. When making socks, for example, it avoids an uncomfortable seam pressing on your heel and toe.
When I was writing the patterns for Crochet Yeah! I had two that would really benefit from a seamless join, the Malvern cowl which is worked in double crochet and Evesham socks worked in half treble crochet. It was the excuse I needed to sit myself down and thrash out a method for each.
I'm pleased with the results of my experiments and I shared the method in the book. This technique is so useful and creates a great finish on lots of different projects and it is always nice to have a visual step by step tutorial so without further ado here is how to graft half treble crochet.
Thread a doubled length of yarn through a yarn needle.
Insert needle from front to back through the top of the stitch on the last row furthest from you.
Insert needle around the post of the last row on the side nearest to you from right to left, front to back to front again. (the same way you would insert your hook to make a raised front (front post) stitch.)
Pull yarn most of the way through stitch but before the loop closes, pass needle between the two strands of the stitch as you tighten it up.
Repeat steps 1-4 for each stitch.