Well, a couple. The orange looking leather I was trying to make for my SOG Seal Pup. Well we see how that worked out. I really wanted a very slimline sheath, and I cut the width too shy. Got it all sewed up (without checking first), brought the black dye just up to the stitch line, then found out there was no way on this green earth that SOG was going in that sheath. Picked up my son's old Kabar with laminated wood grip and ..... sssssnick! Just like I had measured his knife instead of mine.
Next attempt: Cut it right, sewed it right, tried to put it in a low temp oven to dry (170 deg.), didn't leave it very long, came out looking sort of like a six month old banana.
THIRD! attempt is the black one here. Made myself a comfortable, slim, lightweight, left hand sheath. FINALLY! Me likey.
Sometimes the process of learning sucks.