People keep arguing about garter tab cast on..."Why?" "What is it for?" "Why bother?" "Is it hard?"
Here are my two samples. I messed up the lace, the same way, after the cast on, there are eyelets on the right, but not the left, but both pieces have exactly the same lace pattern.
This first one is after a plain, knitted on cast on, of 5 sts, two rows knit, increased by two, to 7 sts, and then the lace pattern.
See? It has a horizontal garter ridge, above a knitted on cast on, with garter ridges to either side. The cast on interupts the pattern of the garter ridge border. I had to pin down the cast on edge, in the middle, quite firmly, as it wants to curve inwards, quite dramatically. I don't expect that blocking will maintain the straight edge for long.
This second one has garter ridges going straight across. You can only tell where the cast on was by where the tail is.
It has a 2 st, prov cast on, 6 rows of knit, pick up 3 then 2 sts, giving 7 sts, then the same lace pattern. This edge is nice and straight, even not pinned out. It's absolutely flat, and since I used a provisional cast on, there are no lumps or ridges, expect for the actual garter stitches.
Here is what I expect them to look like after blocking.
Regular cast on....see the inward curve? That probably won't stay blocked out.
Garter tab....nice and straight!
These spots I showed are the center neck, the center of the long side of the triangle. The garter tab does a bit of magic, and allows the edge to be one, continuous strip of garter stitch, while the regular cast on has a small break in the center of that side. It's a minor detail, but as it takes about 3 minutes to work, as the regular cast on takes about 3 minutes to work, I think the (not extra) effort is worth it!