In that day, saith the LORD of hosts, shall the nail that is fastened in the sure place be removed, and be cut down, and fall; and the burden that was upon it shall be cut off: for the LORD hath spoken it. Isaiah 22:25
" I discovered an even older custom when I realized that hundreds, if not thousands, of nails were pounded into the Western Wall. Older texts reveal a now-forgotten custom of the “sure nails.” This was the practice of bringing one’s sins, grief, or the tragedies of life to the remains of the Temple wall and “nailing” them in a sure place. The nails are a reminder of Isaiah’s prophecy that man’s burden will be removed when the nail in the sure place is taken down."
Daniel Rona- given in a presentation about Israel.