To measure the height of an object that cannot be measured by ordinary means---a house, tree or a homemade rocket---you can use a theodolite. Constructing your own theodolite is easy and inexpensive, and you can have lots of fun determining the heights of various objects in your neighbourhood.
Align the centre of the flat edge of the protractor with the centre of the long edge of the wood or cardboard.
Firmly attach the protractor to the wood or cardboard using the push pin or nail. You may be able to push the push pin or nail in by hand, or you may wish to use a hammer. Take care to avoid breaking the protractor or shifting it out of position.
Attach the weight to one end of the string. Attach the other end of the string to the push pin or nail.
Thinner string will help you read the angle more accurately when using the theodolite. A tangent table, found in a trigonometry textbook or online, will simplify the mathematics of using the theodolite.
Homemade theodolites should not be used with precision is crucial, as in engineering or surveying.