Mr. Radley cements the knot hole shut.
As the tree grows, the knot hole can become covered up by new growth or get pushed out over time. The wood around the knot hole may also continue to grow and expand, filling in the space where the knot hole used to be.
Through a Knot Hole - 1915 was released on: USA: 10 January 1915
The cast of Through a Knot Hole - 1915 includes: Billie Ritchie
Jem and Scout find a ball of twine in the knot hole the third time they visit.
The knot hole in the tree likely rotted away over time due to exposure to the elements, insects, and decay processes. As the wood around it deteriorated, the knot hole eventually disappeared or collapsed, leaving a void in the tree.
It's possible that someone else discovered the items in the knot-hole and took them, or the items were removed or destroyed by an animal or the elements. Additionally, the person who originally placed the items in the knot-hole may have decided to retrieve them for some reason.
Boo Radley was the one who was leaving gifts for Jem and Scout in the knot hole of the oak tree.
Because a tree knot hole normally is the diseased part. Most trees would be able to fight the disease, and the knot hole would be a helpless lump, but in some cases, filling the hole with cement can stop the disease from traveling. If you are talking about To Kill A Mockingbird, Mr. Nathan did it to stop Boo from communicating with the outside world
Arthur "Boo" Radley
he wanted to see a duck in the hole so he was mad about it
Mr. Radley fills in the knot hole