Ninety-degree brackets are couplings used when connecting components such as extruded aluminum extrusions at 90-degree angles. Different varieties of couplings are available for different objectives. Ninety-degree brackets come in a number of different shapes. Examples include tabbed brackets (with projections on the connecting surfaces), extruded thick brackets (designed to look like part of the frame), thin brackets (thin and compact types) and triangle brackets (enabling more sturdy connections). There are also bracket varieties with a number of different added features. Examples include single-surface slotted-hole brackets (with slotted holes in one of the mounting surfaces), covered brackets (with a dust-proof cover), nut-fastened brackets (eliminating the need for nut position fine-tuning) and single-gusseted brackets (enabling easy fastening with a hex wrench).