Ah so its for the lifting gantry/arm will it be fixed or removable ?
Pretty close. So, I am going to use a small chain block and tackle which lives in storage when not in use. There'll be two eyes. One on the body and one on the bumper. When needed I put the pulley block in place, take the weight, pull two pins, and lower the bumper to the ground. The pulley block has reasonably long chains which I want to keep long... The hole is to allow the excess chain run through the bumper without wrecking the paint on top!
The reason I want to keep the chain long is because there will be a similar setup in the front of the habitation box. There'll be a place to screw an eye into the ceiling directly above the gearbox, so I have the ability to get the gearbox out on my own and lower it to the floor. This is something I had to do once before in Durban and it worked very well! There'll be more on this later in this thread.