A 14-year-old boy was trapped for almost two hours in an elevator shaft in the Lafayette Courts housing complex. The youth, Kevin Glenn, was jumping on to the top of the elevator car when he slipped, wedging his right leg and hip between the car and the wall of the elevator shaft. Firefighters rescued him with the help of air bags, electric saws and dishwashing liquid. He was in critical but stable condition last night at Johns Hopkins Hospital. See article, 1B.