At my woodshop, a lot of the workbenches have holes in the tops. I'm told these are for "bench dogs". What are bench dogs and how do they work? Why they're called "dogs".
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Two specifications are available,3/4 inch (19mm) post and 20mm post,this fits perfect for your workbench dog holes. Use this adjustable bench dog
DDWT Adjustable Workbench Bench Dog Screw Clamp Fits 3/4 Inch Dog Holes Stainless Steel Brass Adjustable Stop for Woodworking (19mm)
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Shopmade Bench Dogs
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Levoite™ MFT Style Workbench Bench Dogs Adjustable Clamp Black Toggle — levoite