Abstract: A retainer for retaining an electronic module, such as a printed circuit board, in the slot of a casing. Oppositely oriented wedge-shaped elements are slidingly received on a rail in a manner which prevents rotation of the wedge-shaped elements about the rail. A pivotable lever having a cam surface is provided such that rotation of the lever actuates the retainer by compressing the wedge-shaped elements. In one embodiment, the lever is provided with a projection which engages the casing to extract the module when the lever is pivoted to release the retainer.