Part #3031 is often known as Plate 4x4.
We know this part is available in LEGO Digital Designer, LDraw, Brickset, Bricklink, Rebrickable and Mecabricks.
You can buy it on Amazon or Bricklink.
Steve and John did their job every day, yet they never stopped to consider that their tools might be too small for the task. After all: everything is cool when you're part of a team.
It's a pretty standard site search, but I'm trying to make it smarter day by day. You can currently search for techniques, parts, sets and contributors. If you can't find what you're looking for contact me and I'll try to help you along and make this better.
ALT + F Open search