[tempest]

Sounds like you're talking about a mast step and a Turnbuckle

You didn't say what boat you have, it would help in identifying the correct parts.

https://www.google.com/search?q=mas...marine.com%2Fsonar%2Fsonarparts.shtml;400;366

http://www.horizonhobby.com/product...7&cadevice=c&gclid=CKrhrOa22b4CFe07Ogodc3wAOA