Commonly things such as carpets, hay/ straw and plants are used to hide traps or areas. As mentioned though you could use item kinds and stretch them, however depending on what you use, the textures will likely look stretched which doesn't look great tbh. Personally I stick with the above, and sometimes I make use of building props by having a stair inside a normally non enterable building taking you through the door of a building from inside- it acts as a one way wall, and can only be used in specific instances