When placing blocks, keep these things in mind: if you have a single strong block next to a few weaker blocks, monsters will simply go around the strong block and attack the weaker blocks to get through. This means that the strong block will never serve its purpose. Make sure to build a wall of blocks of the same level in order to best channel the monsters into Booby Traps and away from your resources. Booby Traps should be used with blocks, since as monsters go through gaps in a wall, Booby Traps will destroy monsters before they even get close. However, it is a good idea to place more than 1 Booby Trap as more advanced players will take out Booby Traps with low-level monsters - "minesweepers" (e.g Pokeys). Moreover, Ichi can survive damage taken from Booby Traps.
Try placing your blocks in front of defensive towers, giving them more time to attack the monster while the block is being destroyed as a decoy. Another effective use of blocks is to lead monsters into certain areas away from your resource towers, or straight into traps. A level 1 Champion can destroy a level 1 block in one hit, so it is best to finish upgrading your blocks to level 2 at level 6 Town Hall (earlier if possible, but not too early). Note that they can be extremely expensive to upgrade (if you have a lot of them). Remember, a block from lvl 4 to lvl 5 is 400k Twigs and Pebbles.
Later in the game, they will be used for pathing and Eye-ra bait but not so much for protecting. Upgrading to gold or black diamond (levels 4/5) is mainly just for decoration. You should design your walls so that monsters don't really attack them and go around them instead.
List of Quick Tips
- Use blocks to create barriers around essential buildings and protect them from enemy monsters attack.
- Blocks can be upgraded from wood to stone to metal to gold.
- Invading monsters can't get through blocks placed next to each other, but they can destroy them.
- Monsters can slip between Blocks that are placed on a diagonal.