If you want to mount two signs back to back on a single pole, you can use back-to-back clips that are specifically designed for use with 76mm, 89mm, or 114mm rigid clips
It's important to note that these clips cannot be used with universal clips because of their fixed length
Back-to-back clips work by attaching to the back sign's rail and securing it to the space on the edge of the rail left by the 'D'-clip
To mount two signs back to back, you will need two sets of back-to-back clips and two rigid 'D' clips