Gibson J45 and LG3 guitars from the late 40’s have black cotton cloth strips glued to the sides. These strips are perpendicular to the grain of the sides. I use the word "glued" advisedly because by now there is very little if any adhesion in whatever glue they used. Looks like they used some sort of clear adhesive. Maybe Duco? Whatever it was, adhesion failed.
OK, you say, just rip out the strips. They don’t serve any purpose anyhow. Well here is the problem: the strips extend under the liner blocks at both ends. In effect, the cloth prevents the liner blocks in those locations from adhering to the sides. A section of liner block is easily removed by cutting away the paper thin mahogany connection between adjacent blocks. The blocks practically fall out. A piece of the cloth strip is usually stuck to the block, or to the side.
The image below shows a liner block that I just popped off. Beneath it you can see the glue residue extending up and off image were the cloth strip was glued down. The remains of the cloth strip is still stuck to the liner block. Note the gap in the liner blocks where the little block section was removed. Note that this area is mostly clear of glue residue.
I have removed, cleaned, and reglued every liner block with the above problem around the back of this guitar.