To craft 2 Stone Windows at once, you'll need (as of R26 in December 2015): * 2 (blocks of) Glass made of Sand in a Forge * 4 Stone Rods made of Stone, Limestone or Bedrock in a Processor or found in Stone Treasure Chests * 4 Stone Slabs made of Stone, Limestone or Bedrock in a Processor By crafting/taking Stone Windows for the first time, the recipe for Barred Windows will be unlocked.