Heliana's Guide to Monster Hunting, pg. 220
An expert with your chosen tools, you can subtly alter an item’s final form.
• Increase your Strength, Dexterity, or Constitution by 1, to a maximum of 20.
• When you make a Manufacturing check with a tool with which you are proficient, your proficiency bonus is doubled.
• When you forge an item and roll for enchanting and/or manufacturing quirks, you can apply a bonus or penalty to the result of the roll equal to half your proficiency bonus.
• Each hour you spend forging an item counts as 2 hours towards the item’s completion.