Test tube racks are commonplace in school science labs and are used routinely to securely hold test tubes or boiling tubes that are being observed or filled.
Several types are available from suppliers. Solid wooden constructed racks are generally stable and robust although may get stained by chemicals and liquids. Cheaper types consist of wooden and plastic side parts which can be removed for storage. These side panels should be fitted securely to ensure they do not fall off during use.
Metal racks (usually of a 'z' shape) are used in waterbaths to hold tubes whilst being warmed in the water. These may need to be cleaned routinely as scale and grime can build up on them. Over time the metal types may lose their lustre so take them out of the waterbath when not in use and make sure they are completely dry when in storage.
Solid wooden blocks with holes in are sometimes used in schools to hold test tubes. These can be purchased or easily made by drilling the appropriate sized hole into a solid block of wood. MDF or chipboard should not be used to make this type of holder as they absorb water and will swell up.
'tube cages' are used to wash tubes in a dishwasher. They come in various sizes and shapes and enable tubes to stand upright to be cleaned. Most are of a plastic construction but some are made from metal wire coated in plastic. Damage to these may occur over time resulting in exposure of the metal wire which may then rust. If rusting occurs these units should not be used in a dishwasher.