A modular system for producing an electronic device includes: a housing, which forms an accommodating space; a printed circuit board which is insertable along an insertion direction into the accommodating space of the housing and, in a mounting position, is accommodated in the accommodating space; and a plurality of attachment parts, which are connectable to the printed circuit board and which, when viewed along the insertion direction, each have a division corresponding to a predetermined smallest dividing unit or an integral multiple of the predetermined smallest dividing unit. Each attachment part has a first guide device for guiding on a second guide device of the housing and a combination of attachment parts is connectable to the printed circuit board in a manner arranged next to one another along the insertion direction such that when the printed circuit board is inserted into the accommodating space, the combination is guided.