[Wikipedia excerpt: ‘….Test tube racks are laboratory equipment used to hold upright multiple test tubes at the same time. They are most commonly used when various different solutions are needed to work with simultaneously, for safety reasons, for safe storage of test tubes, and to ease the transport of multiple tubes. Test tube racks also ease the organization of test tubes and provide support for the test tubes being worked with…Test tube racks come in a variety of size, composition, material, and color. The variety of test tube racks increases the number of circumstances they can be used in whether it is to be placed in an autoclave, or to be placed in the refrigerator. The racks are most commonly made of metal wires, but they can also be found as plastic, polystyrene, foam, fiberglass, and polypropylene. Test tube racks come in the form of a classic rack, an interlocking cube form, a stack-able form, test tube drying rack, slant rack, and 1-well rack…..Classic rack…The classic racks are normally found in any regular laboratory and are made of wood, stainless steel, or plastic. It generally has 8 holes, 10 holes, or 12 holes to keep test tubes.
Interlocking cube form…This form of test tube racks consists of several cubes of racks that are detachable and twist-able based on the side that is needed for use. Each cube can hold one size of test tubes but each of the four sides of the cube holds the tubes in various arrangements that can be adjusted for use accordingly. These racks can not only be used for test tubes, but it can also be used to hold culture tubes, centrifuge tubes, and micro-centrifuge tubes. The interlocking cube racks can also be put in the autoclave, as well as ease the transport of multiple different sized tubes.
Stackable rack…Stackable Test Tube Rack…Stackable racks are made of polypropylene and can be placed in the autoclave as well. Using a secondary frame or chassis these racks that otherwise appear as the classic test tube racks can be placed one on top of the other.
Test tube drying rack…Drying Racks can be used for various purposes, including drying and holding chromatography plates, as well as drying test tubes by placing them in an inverted position in the pegs…..’]