Kable needle holder - instruction help

Can someone help me decipher these instructions? I just can’t get a visual.

Kable felted needle case

“A large flat piece like this tends to get a lettucey ruffled edge when felted. To keep side edges pulled in, thread a strand of yarn into tapestry needle and weave in and out along both side edges of body. [B]Pull strands gathering side edges in to 1/2 of their original length, anchoring strands every 5”.[/B]"

ETA: I think (after reading this about 17 times) I finally understand what they are saying.

Yes, I think you have it right.

Apparently your project tends to have wavy, up-and-down edges due to extra, unneeded material.

Threading a single strand of yarn straight through these edges gives you the ability to snug them in until they lay nice and flat. Since a straight strand only stretches a certain amount, this is an excellent fudge to resolve wavy edges.

Another way would be to put an edging of single crochet around the offending edge - and space the single crochet stitches wide apart. This also would bring the offending waviness under control - but this way wouldn’t be likely to fit in well with all patterns.

Dot