  Fragile topology, akin to twisted bilayer graphene and the exotic phases
therein, is a notable topological class with intriguing properties. However,
due to its unique nature and the lack of bulk-edge correspondence, the
experimental signature of fragile topology has been under debated since its
birth. Here, we demonstrate experimentally that fragile topological phases with
filling anomaly can be probed via screw dislocations, despite that they do not
support gapless edge states. Using a designer hexagonal phononic crystal with a
fragile topological band gap, we find that 1D gapless bound modes can emerge at
a screw dislocation due to the bulk fragile topology. We then establish a
connection between our system and the twisted boundary condition via the gauge
invariance principle and illustrate that such an emergent phenomenon is an
intrinsic property of fragile topological phases with filling anomaly. We
observe experimentally the 1D topological bound states using the pump-probe
measurements of their dispersion and wavefunctions, which unveils a novel
bulk-defect correspondence of fragile topology and a powerful tool for probing
fragile topological phases and materials.
