Ground glass joints of borosilicate glass pyrex are used in laboratories to quickly and easily fit leak-tight apparatus together from commonly available parts. For example, a , , and with ground glass joints may be rapidly fitted together to a reaction mixture. This is a large improvement compared with older methods of custom-made glassware, which was time-consuming and expensive, or the use of less chemically- and heat-resistant or and glass tubes as joints which took time to prepare as well.

To connect the hollow inner spaces of the glassware components, ground glass joints are hollow on the inside and open at the ends, except for stoppers.