Synclastic: "Curved in all directions towards the same point" Anticlastic or Anti-Clastic: "Similar to synclastic but produces a concave curve instead of a convex curve".
Used in the process called anticlastic raising. This is the 11" long (medium length) Sinusoidal Stake.
Steel Sinusoidal stakes are commonly used with plastic or nylon hammers like our "Bossing Mallets or Pimentel Style UHMB Raising hammers". For a textbook that covers this work, please see "Form Emphasis" by Heiki Seppa (BK239)"