What is the definition of test tube holder?

A test tube holder is an apparatus designed to support and store test tubes during a scientific experiment. A test tube is a thin-glassed tube with one closed end used in the examination of cultures such as bacteria. Test tube holders may also be referred to as test tube racks.

In addition to support and storage, test tube holders allow organization of test tubes. Other uses include transporting of tubes and holding other lab tools such as pipettes and stirring rods. Test tube holders may be made from a variety of materials such as plastic, polypropylene and aluminum. They may also be built to accommodate varying numbers of test tubes.