We have investigated the vortex structure in three different represent
atives of highly anisotropic layered superconductors: T12Ba2Ca2Cu3O10,
Bi2Sr2CaCu2O8 and kappa-(BEDT-TTF)2-Cu[N(CN)2]Br. Based on the equili
brium part of the magnetic torque we identify the vortex lock-in trans
ition, i.e. the perfect alignment of the magnetic induction parallel t
o the superconducting planes. This Meissner state for pancake vortices
is quantitatively confirmed by ideal screening of the perpendicular f
ield component.