This lecture delves into the kinematics of 3D structures based on the Kirchhoff equation, exploring twisted solutions and recent developments in rod mechanics, including the mechanics of knots. The presentation covers the framework of the Kirchhoff equation, differential geometry of curves, and the relationship between moment and strain. It also discusses force and moment balances, the use of the Kirchhoff equation, and the derivation of equations for the Darboux vector. The lecture concludes with examples of kinematics, twisted solutions, and the implications of elasticity and geometry in rod mechanics.