Try this shirt thumbhole design from Threads Digital Ambassador Becky Fulgoni. It is sturdier than in-seam versions and better placed to accommodate each thumb.
Sew Sturdier, Better-Placed Thumbholes Into Sleeves - Threads
Simply crochet issue 41 2016 by Maika Sadith - Issuu
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Kezzled- Protective Arm Sleeves for men or women with Thumbhole, Cut/Scratch/Heat Resistant Arm sleeves with UV Protectors Safety for Garden Kitchen Work – Black-18Inches Made with Kevlar by DuPont : Tools
Sew Sturdier, Better-Placed Thumbholes Into Sleeves - Threads
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