// Return false if there's an entity blocking the placement.
if (!world.canPlaceEntityOnSide(blockBackpack, x, y, z, deathDrop, side, carrier, backpack)) return false;
// Return false if the player can't edit the block.
if ((player != null) && (!world.canMineBlock(player, x, y, z) ||
!player.canPlayerEdit(x, y, z, side, backpack))) return false;
// Do not actually place the backpack on the client.
if (world.isRemote) return true;