Spell & Trap Card Zones are the boxes with "5" in them. You can only have in play at any one time, 5 face-up or face-down Spell Cards and/or Trap Cards, with an additional Field Spell Card If you have all 5 Zones occupied, to activate another Spell Card, or to Set another Spell/Trap Cards from your hand, one of your Spell/Trap Cards needs to be removed from the field.
Gameplay and Glossary