A part includes a first member and a second member including an engagement portion engaging with an engagement protrusion of the first member and restricting separation of the first member in a predetermined direction with respect to the second member. The engagement portion includes: a facing portion facing the engagement protrusion from downstream in a separating direction of the first member with respect to the second member; a first coupling portion connected to one end of the facing portion and coupling a main body of the second member and the facing portion to each other; and a second coupling portion connected to the other end of the facing portion and coupling the main body and the facing portion to each other. The second coupling portion includes an escape portion in which the engagement protrusion is movable in the separating direction and an orthogonal direction to the separating direction.