In pure SU(3) gauge theory above the deconfinement temperature, spontaneous breaking of center symmetry
produces multiple $Z_3$ sectors separated by interfaces. A junction of these interfaces supports a line-like
defect where the Polyakov loop is forced toward zero.
Using Monte Carlo simulations at $N_\tau=2$ on
$60^2\times 4$ spatial volumes, we compute the defect free energy.
We find that the dominant contribution to the defect tension originates from the attached interfaces,
and that near the transition the configuration is strongly affected by confined--deconfined interfacial
fluctuations.

