Guiding transports of classical waves has inspired a wealth of nontrivial physics and momentous applications in a wide range of fields. To date, a robust and compact way to guide energy flux travelling along an arbitrary, prescheduled trajectory in a uniform medium is still a fundamental challenge. Here we propose and experimentally realize a generic framework of ultrathin waveguides for full-angle wave trapping and routing. The metagrating-based waveguide can totally suppress all high-order parasitic diffractions to efficiently route guided elastic waves without leakage. Remarkably, the proposed waveguide protype works in a broad frequency range from 12 to 18 kHz and regardless of the incident angle. An analytical slab-waveguide model is further presented to predict and tailor the diffracted patterns in the metagrating-based waveguide. Compared with existing methods based on topological edge states or defected metamaterials, our meta-waveguide strategy exhibits absolute advantages in compact size, robust performance, and easy fabrication, which may provide a new design paradigm for vibration control in solids, wave steering in electromagnetics, acoustics and other waves.