Are you building your own custom DL-44 blaster? The model Mouser from the Denix Corporation is commonly used as the base. If you are looking to add lights and/or sounds, this is the part for you!
This piece is meant to hold a lever switch (see pics) that can be used as the trigger for your effects module. For the switch to properly fit, the three leads need to be trimmed down approx. 1/4 of the their length. The switch will have a nice pressure fit but it is recomended that you apply a bit of hot glue or a similar adhesive on the sides for extra support. The holder can also be held into place by adding some adhesive between its side and the interior wall of the Denix. See the last picture to see how your holder should be setup.