  Two-sided flux decoration experiments indicate that threading dislocation
lines (TDLs), which cross the entire film, are sometimes trapped in metastable
states. We calculate the elastic energy associated with the meanderings of a
TDL. The TDL behaves as an anisotropic and dispersive string with thermal
fluctuations largely along its Burger's vector. These fluctuations also modify
the structure factor of the vortex solid. Both effects can in principle be used
to estimate the elastic moduli of the material.
