Lots of Steel crates! is the 2nd and final level of the Tricky difficulty from the Lemmings demo disk Save the Lemmings.
Strategy[]
Make the first two Lemmings Climbers. Make the first a Bomber when it gets at least halfway up the second box. The second should build immediately after turning left in the crater, and reach the Exit portal platform. Make all other Lemmings climbers while they are walking right.
Solution