I'm just slightly better than a beginning knitter. I am getting to the final step of a messenger bag. It was done in stockinette stitch, two rectangles with one (the back) being twice as long as the other (the front) to create a flap. There is a long strap/gusset to connect the front to the back and also to make two straps, one being longer than the other, which after felting will be tied together. The strap/gusset was 12 stitches wide in a stockinette. I've finished everything. The bag is complete with front and back connected and 2 straps. However there is one step left before felting. There is supposed to be contrasting trim (B) that runs along the long edges of each strap and along each side of the flap (I have already knit B as my first 2 rows of the flap, then switching to my main color). I am unsure how to attach B to the straps and the flap. Here are the instructions:
From RS, with B, pick up and k 100 sts along side edge of shorter strap. Purl 1 row. Bind off. Repeat for opposite edge. From RS, with B, pick up and k 140 sts along side edge of longer strap. Purl 1 row. Bind off. Repeat for opposite edge. From RS, with B, pick up and k 54 sts along side edge of back flap. Purl 1 row, Bind off. Repeat for opposite edge.
How do I "pick up and knit"? Why is it 100 and 140 and 54 stitches exactly rather than the length of the strap and the flap? The front and back and strap were all knit according to length (14", 28", and 104" respectively), so I don't even know how many stitches are along each side.
According to the picture the trim is supposed to look as if it were knit as part of the original pieces. For each row of the flap, it should be 2 stitches of B then 64 stitches of A then 2 stitches of B. For each row of the straps, it should be 2 stitches of B 12 stitches of A then 2 stitches of B.
I'm really confused and would VERY MUCH appreciate some help from experienced knitters!
Thank you so much!