3 cestus can be crafted with the following recipes

Player Recipe
Primary skill used: fabrication(2)
Required skills: bashing(1)
Time to complete: 30 minutes
Tools required:
> 1 tool with hammering quality of 1
> 1 tool with metal sawing quality of 1
> 1 tool with sewing quality of 1
> 1 tool with cutting quality of 1
Components required:
> 4x leather patch
> 8x scrap metal
> 5x thread OR 5x sinew OR 5x plant fiber OR 5x yarn OR 5x Nomex thread OR 5x Kevlar thread
Byproducts:
(none)
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This recipe can be found in the following books when fabrication is at least the required level:
The Streetfighter's Sidekick (level 1)
The Swords of the Samurai (level 7)