Caltrops were medieval area-denial weapons made up of sharp spines arranged so that one of them always points upward. They slowed the advance of troops.
Medieval Caltrop Defense Weapon Coming to the Aid of Ukrainian
Caltrops (MISC635)
Original Vintage Military Issue Steel Caltrop – International
Caltrop. Caltrops or crow's feet were scattered on the deck of
Caltrop Weapons
Sold at Auction: 10 MEDIEVAL LARGE CALTROPS (CROWS FEET) CALTROPS.
Civil War Caltrops – Old as Adam
Caltrop - Wikipedia
Medieval Weapons: Caltrops. Types of Caltrops, Facts and History
Medieval Weapons That Maimed and Killed
The Caltrop: A Weapon That's Barely Changed Over 2,300 Years
Medieval Weapons: Caltrops. Types of Caltrops, Facts and History
The Caltrop: A Weapon That's Barely Changed Over 2,300 Years
Caltrop, Military Wiki