This tool is called a "Sailor's Palm" and is essentially a strap fashioned of leather and bone. It protects one's palm when pushing large needles through layers of sailcloth or leather and would have been a staple for a sail maker or harness maker. The dimpled indentations in the palm would catch the head of the needle and provide reinforcement for pushing it through the multiple layers.
Sailor's palms would have been very common in the Kennebunks' many shipyards. They were typically custom-made to the individual user. The example pictured here was made for the right hand.
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