It is a mirror on a pickup truck that is braced and is actually an accessory or after market mirror
Remove the inside door panel from your 1991 Chevrolet 1500 pickup truck. Remove the wiring harness from the mirror. Remove the driver side mirror retaining bolts. Reverse the process to install the new driver side mirror.
It is screewed into the drivers side head between the front 2 spark plugs up front.
Starting with the lower aft knob (the one closest to the input jack) and moving clockwise, the controls are as follows: Tone Control for the Bridge Pickup, Tone Control for the Neck Pickup, Volume Control for the Neck Pickup, Volume Control for the Bridge Pickup. The switch (usually located on the upper horn if you're playing a Les Paul) is used to switch between the pickups. Hope this was helpful!
drivers side door jamb
1960 Chevrolet pickup. Just got one for my 1970 GMC pickup. Looks kinda retro.
behind the drivers seat.
inside frame , drivers side
Underneath the drivers side, on the inside of the frame rail, aprox under the drivers seat area.
Above the rear axle, drivers side.