Label holder for a label of 5cm × 2cm, with a 3mm frame holding the label in place. The slit is 1mm high. The slit should be enough room to pry away the support with a tool without detaching the frame. The walls holding the frame are 0.8mm thick at the point where they join. The screw/nail holes are 2mm in diameter.
Removing the support is a bit tricky because leveraging too much the wall may cause the holding frame to detach. Careful prying and low support density help.