Pyle Mobile Video System PLD43MU Owner's Manual page 7

Installation
SPRING WASHER
PLAIN WASHER
TAPPING SCREW
KEY PLATE
If you want to take CHASSIS out of the SLIDE BRACKET HOUSING,
first remove the PLASTIC COVER of the both sides away, then insert
the two KEY PLATE into left and right side of chassis as above illustration.
DASH BOARD
HEX NUT
METAL MOUNTING
STRAP
6
CONSOLE
SLIDE BRACKET
HOUSING
HEX BOLT
KEY PLATE
PLASTIC COVER