Minecraft wiki entry for Multiplayer_details, associated text: To determine the protection area, the player (a non-op) attempted to place blocks until successful while moving away from the spawn, and then traced around the edges of the protected area until all four corners were found. The lapis corners marked above were the extent of the minimum placeable area by the player. The blue square, above, is drawn from the midpoints of the outermost protected blocks in each direction.