When you are trying to add cornerstone OL you should try your best to acquire them as early in the draft as possible. Currently the only Pro Bowl lineman on the Bears was drafted in the first round.One of the best OL in team history had 2 1st rounders, a 4th an 8th and a UDFA. Covert,Van Horne,Thayer, Bortz and Hilgenberg. OL can be found throughout the draft but, when you want to protect the edges invest in early draft prospects IMO.