That is an upholstery webbing stretcher.
<strong>https://naturalupholstery.com/2015/11/how-to-stretch-upholstery-webbing-using-a-gooseneck-stretcher/how-to-stretch-jute-webbing-gooseneck-stretcher/</strong>
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https://www.amazon.com/Osborne-253-Gooseneck-Stretcher-Upholstery/dp/B002U2RADQ
It is a tool to stretch webbing on the bottom of upholstered chairs.