If you ever need to get through a wall with enemies on the other side, you can make a sachel charge using your grenades and blocks! The blocks make a shelf that holds the grenade at the right level, and it makes a nice 3x3 hole in thin walls :)
The only tricky park is making sure you don't get blown up, I usually put a block in the middle so it covers the grenade, and that usually gives me full protection.
Pic:
http://i.imgur.com/pth8g.jpg