fillRect
fun fillRect(x1: Int, y1: Int, x2: Int, y2: Int, material: Material, pickable: Boolean = false, creator: SlotCreator.() -> Unit = {})
Fills a rectangular area of the GUI with a material.
fun fillRect(s1: Slot, s2: Slot, material: Material, pickable: Boolean = false, creator: SlotCreator.() -> Unit = {})
Fills a rectangular area defined by two slots with a material.