Localized Interaction Approach.- Cavity Expansion Approximations.- Power-Law Realationships Between Impact, Residual and Ballistic Limit Velocity.- Towards Shape Optimization of Impactors.- Shape Optimization of Impactors Penetrating into Ductile Shields.- Shape Optimization of Impactors Penetrating into Concrete Shields.- Optimum Shape of Impactors Against Fibre-Reinforced Plastic Laminates.- Area Rules for Penetrating Impactors.- Optimization of Multi-layered and Spaced Ductile Shields.- Optimization of Two-Component Ceramic Shields.