Aligned nutplate locations to 1/8" thick AL backing plate. Located, drilled, countersunk (with a deburring tool), and riveted nutplates with soft solid rivets. Located backing plate on FW, drilled 1/8" pilot holes, enlarged to 3/16" with step drill. Deburred back end of stainless firewall with the step drill. Mounted the terminal block with #10 screws, aligned to approximate center of through hole and tightened mounting screws to hold the backing plate. Drilled two of the four mounting plate holes for CPP-34 blind rivets. Installed with hand rivet tool.