Support brackets for an enclosure system can be secured to the enclosure system while the enclosure system is assembled and without removing fasteners from the enclosure system. A support bracket can include first and second slots dimensioned to engage first and second bolts that are fastened to an enclosure frame. The support bracket can further include a support flange, and a stud to engage and support a side panel. When secured to the support bracket, the side panel can provide an additional mounting surface for mounting electrical components within an enclosure.