Modifiers matching boot:

• athletic,
• weather,
• automotive,
• conventional,
• waterproof,
• studded,
• ordinary,
• organizational,
• heavy,
• larger,
• dry,
• large,
• rigid,
• harder,

Simple categories matching rigid:

• material,
• surface,
• rod,
• deck,
• hitch,
• paper,
• document,
• adhesive,
• shaft,
• block,
• container,
• class,
• object,
• airfoil,
• structure,
• strip,
• substrate,
• item,
• polymer,
• body,
• plant,
• obstruction,
• feature,
• sphere,
• textile,
• pavement,
• frame,
• system,
• lining,
• plastic,
• fixture,
• sector,
• shape,
• tissue,
• element,
• fiber,
• profile,
• casing,
• coil,
• fastener,
• change,
• tube,
• layer,
• medium,
• product,
• matrix,
• post,
• piece,
• component,
• floor,
• obstacle,
• article,
• stick,
• part,
• group,
• construction,
• movement,
• carrier,
• panel,
• connector,
• pipe,
• member,
• metal,
• appliance,
• boundary,
• transparency,
• architecture,
• display,
• tubing,
• sheet,
• support,
• organs,
• deposit,
• cloth,
• protein,
• gel,
• thermoplastic,
• cutoff,
• representation,
• organ,
• sorbent,
• splint,
• watercraft,
• molecule,
• rock,
• foam,
• filler,
• substance,
• web,
• insulation,
• monomer,
• space,
• cement,
• motion,
• luggage,
• macromolecule,
• resin,
• aggregate,
• dressing,
• fixing,
• alteration,
• fabric,
• instrumentation,
• barrier,
• fibre,
• plate,
• entity,
• cylinder,
• wall,
• appendage,
• food,
• boot,
• measure,
• package,
• particle,
• instrument,
• thread,
• transformation,
• connection,
• base,
• portion,
• covering,
• tip,
• mineral,
• vehicle,
• ground,
• bottle,
• packing,
• foundation,
• finish,
• devices,
• tool,
• case,
• device,
• means,
• form,
• matter,
• mechanism,
• unit,
• bed,
• implement,
• hanger,
• armour,
• cover,
• solid,