this will explain how to and show how to restretch a whole house of carpet
https://www.thefloorsbysouthernboys.com/

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Here are links to a few of the tools used in this video!

power stretchers
https://amzn.to/2Iv1IsJ

knee kicker
https://amzn.to/2DZIA0u

updated carpet trimmer
https://amzn.to/2GUQBXH

stair tool/packer
https://amzn.to/2E4gUrh

carpet knife
https://amzn.to/2V6XhFO