Thanks for posting. Were there no bi-fold door pins on this door when you bought the house? That will make identifying what you need difficult. Is there another, identical bi-fold door in the house that still has its hardware that we can use as a reference?
Looks like you have the old style National bi-fold doors. I'm afraid that we no longer have the complete spring loaded guide pins. You will need to put them together. They consist of the following parts: the 21-026B pin, the 21-113 cap, 21-252 spring and 21-155 palnut.
The top spring loaded pivot pin would be our 21-026B with a 21-155 palnut pushed on about 3/8" down, then you would place a 21-252 spring below it and put the pin through the door at the top and lock it on with another palnut, our 21-155. The bottom threaded pin would be our 21-046.
