For this task you will need:
a meter stick or a measuring tape
Choose a tree that you would like to measure
One person stands at the tree while the other walks away from it, holding their pencil up vertically and in line with the tree. As soon as the bottom and top of the pencil line up with the bottom and top of the tree, this person should stop moving.
The pencil holder will turn the pencil so that it lines up with the base of the tree horizontally. The person holding the pencil will tell their partner to move away from the tree until they are lined up with the very tip of the pencil.
Measure the distance from the tree to where this person is now standing. This will be the rough height of the tree.