A tougher remix of the "Tricky" level "Lemmingology", with the "U" shaped brick structures and everything. The solution is, of course, different here. You're not allowed to lose even ONE Lemming, so be careful.
First "U" shape is no different from the earlier solution. Build a ramp from the very left. At the second "U" shape, it's a bit different. Have one Lemming (preferably the last one) build a ramp BEFORE the hole! One Builder skill shall be enough to cover it, you just need to apply the skill at the very edge. When the Lemming reaches the other side, give another Builder skill so he can reach the third "U" shape. Inside the third "U" shape, apply a Builder skill close to the right wall. Wait for your Lemming to hit the wall, then apply a Basher skill to take out the right side of the "U" shape - this will make your Lemming drop into the fourth "U" shape without splattering. Use some more Builder skills on him to make ramps that reach the exit.Finally, allow the stuck Lemmings to get out of the hole using Builder skills - you should have more than enough.