Ranger trailer plug ground

[pat13]

2005 Ford Ranger
Does anyone know where my trailer plug grounds to? Dont tell me to check my trailer please. I just plugged it into an other vehicle and worked fine. I just need to know where the ground location is

 

[Uncle Gump]

I believe the ground on my 06 is on the spare tire crossmember

 

[Dirtman]

On my 09 its on the center of the rear most crossmember.