Initially my thoughts were to use 6mm plywood for the runners but not having any suitable plywood to hand rather than buying a small sheet of it i considered other options including 3mm.
Hard drive rack diy.
Diy hard disk expansion bracket hdd 3 5 nas 4 disk external racks support power supply transparent acrylic rack.
7 pin sata x 4 drive fit.
17 32 of 600 results for hard drive rack syba sy mra55006 5 25 bay tray less mobile rack for 3 5 and 2 5 sata iii hdd with extra 2 port usb 3 0 black white 4 2 out of 5 stars 314.
Aliexpress carries many hard disk rack related products including aluminium optibay 20 hard drive orico v1 sata enclosure for ssd ide and sata usb case for external hard drive seagate case for 25 inch ide to usb.
Up to 6 gb sec.
Kkmoon hard drive hdd ssd tray caddy internal mobile rack enclosure docking station dual bay 3 5 2 5 inch sata iii with usb 3 0 port hot swap 4 7 out of 5 stars 9 32 99 32.
Icy dock 4 x 2 5 sata 6gbps hdd ssd mobile rack cage in 1 x 5 25 bay tougharmor mb994sp 4sb 1.
The equipment rack is designed so that the external hard drives will slide into place using the 6mm 1 4 inch groves built into the sides of each hard drive.
Matt black mobile rack drives support.