Issue resolved. http://documentation.extremenetworks.com/summit/downloads/SummitFamily_HW_Install_EXOS21.pdf
The following items are provided with ExtremeSwitching and Summit switches:
• Two rack mounting brackets adaptable for either a front-mount or mid-mount installation.
• Two long mounting brackets (rails) for rear mounting in four-post or cabinet installation (only with
switches for which four-post mounting is supported).