This chapter focuses on the physics of plug formation under low-compression conditions including mathematical modeling, measurement and testing, as well as practical aspects of plug formation during automated capsule filling. Tablets are formed by use of eccentric, rotary, or centrifugal die filling machines, and this affects the resulting density of the tablets, particularly their density distributions. The formation of plugs is fundamentally different in dosator-nozzle compared to tamp-filling machines. Lewis and Shotton found that with some tabletting formulations, the axial force transmission ratio was insufficiently sensitive to distinguish between similar lubricants and that the best lubricants were those with the lowest melting point. In the development of tablet formulations, the recording of ejection forces is very important, as it permits optimization of lubricant concentrations in the formulation. The determination of the mechanical strength of tablets forms an essential test procedure in development and production, in-process, and quality control.