A door assembly includes a hook hole, a door having a hook shaft to be placed in the hook hole, and a holder between the hook hole and the hook shaft for maintaining the door to be in a state the door is opened by a predetermined gap, wherein the holder includes a first holder to be engaged with the door and a second holder to be engaged with hook hole, wherein the second holder includes a hook member for placing in, and holding the hook hole. The assembly, for example, prevents a tub of a washing machine from being enclosed when the washing machine is not in operation.