door post cont
Pic 1, So this fuzzy pic is your door post (technically its the striker bolt), if it was the real thing, the threads on the back side of the washer extend about 3/4" to 1" past, and that would be after there were 2-3 washers there. Those individual washers are probably not as thick as this one is.
Pic 2, This is sort of what the captured nut would look like when attached to the sheet metal on the back side of your door jam. When you are ready to put this in place, the hole in the door jam has to be big enough to fit the captured nut and its cage in so the sheet metal sits flat against the jam.
Pic 3, This would be what you see when you are ready to install the post bracket. When its correct, the threaded nut should be able to float around in pretty much the entire inside hole. The larger washer on the post pulls the nut up against the metal to lock everything tight. When its time to weld, you would be welding only around the outside of the sheet metal (the sanding disc). As one would expect, you want that sheet metal to be tight against the metal you are welding to. Another note here is the outside configuration of the sheet metal can be any shape that fits your door jam, you just want to be sure the door can be closed all the way, so the large washer has to be able to clear anything that might limit its movement, once its welded into place.
One more thought, I use this set up to repair a lot of ripped out striker bolts (because the door hinge bushings have been wore out, and the people keep slamming the door until the post rips out of the jam). I have found that if you screw the post into the nut snug, you can use the post to position the sheet metal in place, and you can hang your welder ground on the post. With the post screwed in, you don't have to be concerned about a weld bb messing up the nut threads, just loosen the bolt before the weld cools.
Just for the record, if you are repairing a striker post that has been ripped out because of worn hinge bushings, be sure the bushings are repaired, or the new sheet metal will tear out within 2 weeks again. If you can lift the handle end of an open door more then 1/8",and feel it slop up and down, the hinges need to be repaired.
Pic 4, A side view of what the striker post and the captured nut and cage look like from the side. Gene