Minecraft wiki entry for Shelters, associated text: These are an easy way to keep mobs at a distance, and are especially effective against mobs which use sight as a weapon, such as creepers and endermen, however it can be tough to collect the necessary resources for this mechanism. Say we're going to protect a window which is two blocks from the ground and four blocks wide. To start, count three blocks out from the window, and then dig a 6-block-wide, 3-block-deep, 3-block-thick (6×3×3) trench, and then line the far edge of the trench with pistons pointing upwards. Next, place three blocks of gravel on each piston so that there is one block of gravel sticking up above the ground. Behind each piston, place a solid block that accepts redstone, and then place a bit of redstone on each of these blocks, as well as the blocks behind them. From there, run a redstone line to the lever which we'll use to work the blast shields, keeping in mind that redstone can accept a signal from the block above it (making it feasible to have the lever inside your house, preferably near the window you wish to protect).