The inventive subject matter disclosed herein provides a retainer apparatus for a luminaire assembly. The retainer apparatus includes a spring clamp unit including a clamp element and one or more first springs. The one or more first springs are coupled with the clamp element and the luminaire assembly. The retainer apparatus also includes a lock spring unit comprising a second spring coupled with the luminaire assembly and the clamp element. The second spring of the lock spring unit secures the clamp element in a released position. Responsive to actuation of the second spring, the one or more first springs move the clamp element from the released position to a locked position to secure the luminaire assembly into a recess.