An apparatus for use in a wellbore comprises a housing having a longitudinal axis and a mechanism having one or more impact elements adapted to move along the longitudinal axis in an oscillating manner to impart a back and forth force on the housing to vibrate the housing. If the medium does not comprise a closed medium, the medium comprises non-commercial medium. Trenches are cut into the epitaxial layer and filled with oxide to provide reduced junction capacitance and reduced base resistance. A first assembly jig supports the panel whilst a second assembly jig holds the side wall in a configuration corresponding to the grooverebate. A latch hook is rotatively mounted on the deck to the rear of the abutting surfaces for engagement with a laterally extending latch bar which depends from the gooseneck, and a pneumatic actuator is operatively connected to the latch hook for moving the latch hook into and out of engagement with the latch bar.