A mechanism for locking boards with various components mounted on them onto the chassis of an electronic device is composed of brackets, which are attached to these boards and which are to be mounted onto the chassis at a series of fixation points provided at certain intervals on it, and a locking element having a number of tongue-shaped pieces. Locking is accomplished by inserting each of these tongue-shaped pieces between a pair of adjacent brackets so that it engages with them. This mechanism requires fewer components than conventional mechanisms and is also easier to operate.