There was a sheet of ice on bottom of my freezer that I removed. There are two white knobs that protrude but can't be turned with my hand and there are 3 other white knobs with really small holes in them, but I have a hard time believing there are screws inside of them. Please advise how to remove the back panel so I can access my drain. If I can figure out how to attach it, there is a picture of my panel.