the black tar like stuff is urethane. Basicly the same stuff that holds the plastic moisture barrier inside your door, and seals the stationary glass all around. You can buy it in "rope" form which is a bit stiffer, and caulk style in a tube (mostly used for glass) both are available from 3M, or your paint(auto) supply... Sherwin Williams in a lot of places...Dupont in others.