Dell PowerEdge R720 Technical Guide - Page 40

The static rails (shown in Figure 15) support a wider variety of racks than the sliding rails, but do not support serviceability in the rack and are not compatible with the CMA. One key factor in selecting the proper rails is identifying the type of rack in which they will be installed. Both the sliding rails and the static rails support toolless mounting in 19"-wide, EIA-310-E compliant square hole and unthreaded round-hole 4-post racks. Both also support tooled mounting in threaded hole 4-post racks, but only the static rails, as the more universal solution, support mounting in 2-post (Telco) racks. Table 23 lists the rack rail systems that the R720 and R720xd support. System Rail identifier B6 R720/R720xd B4 Mounting interface ReadyRails II ReadyRails Rail type Sliding Static Rack types supported 4-post 2-post Square Round Thread Flush Center    X X For detailed information about rail dimensions, see the Rack rail specifications section in Appendix A. For more information on installing the T620 in a rack, see the Rack Installation Instructions on Support.Dell.com/Manuals. 40 PowerEdge R720 and R720xd Technical Guide