Three components contribute to the acoustic field propagating in a wedge or over a ridge : a direct path arrival, an image component due to reflection from the boundaries and a component diffracted by the apex. All three contributions are included in a new, exact solution of the Helmholtz equation for the three-dimensional time harmonic field from a point source in a wedge(or over a ridge) formed by two intersecting, pressure-release plane boundaries. The solution is obtained by applying three integral transforms, and consists of and infinite sum of uncoupled normal nodes. The mode coefficients are given by a finite integral involving a Gegenbauer polynomial in the integrand, which may be computed relatively efficiently. Results of the theory for propagation over a 90 degree ridge is discussed.