To Richards point, molded plastic holders have a light tight lap over at the flap end where wood holders just do not have that option. As a result a piece of black tape over both seems of the flap end are advised as is the dark cloth over the rear end of the camera. On my 8x10, 5x7 and 4x5 cameras with plastic holders the dark cloth is not necessary. With 8x20 and 11x14 and wooden holders the black tape and dark cloth is standard operating procedure.