[76Red18]

It's a wood block to prevent the liner from cracking when the fitting is tightened. I chiseled, dug and scraped the rot out with a bent screw driver. I then put duct tape over the hole on the hull outside and filled it with a mixture of resin and wood flour from the inside. Make sure you fill the whole void. Let it harden and then re drill. I chose a larger size bronze fitting that accepts a standard bilge plug. If you had a mysterious leak thats probably it.