If you have the small sofa slide like my 28 BHS, you open the cabinet over the sofa and it goes between the trailer inner wall and the top of the slide, inside the hole in the top of the opened cabinet. It has to be tightened by turning by hand to lock it tight between the wall and the slide. I`m surprised they never used it as the slide can move in and out at the top quite a bit without the lock in place.
2017 Coachmen Catalina 283RKS
2018 Ford F250 Super Duty 6.2l CCSB
2010 Jayflight 28BHS (sold)