As an alternative i could always mount the sub panel on the adjacent wall so that it s facing 90 degrees to the main panel.
Mounting a sub panel to a concrete basement wall.
If the back of the panel was flat i d definitely use plywood.
Very low water table area.
Basement is always dry no sump pumps no moisture coming through foundation wall.
And the shorter distance between the two panel means a cheaper installation.
Then remove the tape.
Only 1 8 or so but it keeps the moisture out.
Just a drill and a piece of wood will.
Since the sub panel is only 14 wide i will still have at least 3 of space between it and the main panel as well as between it and the adjacent wall.
I am showing a cheap trick when you don t want to spend the money on expensive dowels or specialized mounting devices.
Tape a one foot by one foot square of plastic sheeting plastic kitchen wrap will do to the concrete wall in your basement with duct tape and leave it in place for 24 hours.
The basement is finished but foundation walls are bare concrete electrical stuff is surface ac cable when it needs to provide outlets and devices on foundation wall.
This just makes sense because you connecting the sub panel directly into the existing panel.
I usually use tapcons.