Modifiers matching opening:

• outer,
• rectangular,
• natural,
• small,
• larger,
• vertical,
• narrow,
• trim,
• exterior,
• operational,
• circular,
• epidermal,
• curved,
• developing,
• structural,
• off,
• mechanical,
• permanent,
• adjacent,
• necessary,
• fixed,
• smaller,
• surrounding,
• over,
• framed,
• gothic,
• external,
• prepared,
• close,
• large,
• symmetrical,
• outside,
• typical,
• horizontal,
• fine,
• architectural,
• conventional,
• underground,
• decorative,
• important,
• accessible,
• outdoor,
• size,
• fleshy,

Simple categories matching rectangular:

• object,
• pan,
• box,
• item,
• area,
• waveform,
• wave,
• block,
• screen,
• room,
• obstacle,
• form,
• surface,
• image,
• defect,
• composition,
• product,
• structure,
• package,
• thing,
• article,
• group,
• opening,
• shape,
• solid,
• container,