Abstract. B. Blackadar recently proved that any full corner pAp in a unital C*-algebra A has K-theoretic stable rank greater than or equal to the stable rank of A. (Here p is a projection in A, and fullness means that ApA = A.) This result is extended to arbitrary (unital) rings A in the present paper: If p is a full idempotent in A, then sr(pAp) ≥ sr(A). The proofs rely partly on algebraic analogs of Blackadar's methods and partly on a new technique for reducing problems of higher stable rank to a concept of stable rank one for skew (rectangular) corners pAq. The main result yields estimates relating stable ranks of Morita equivalent rings. In particular, if B ∼ = End A (P ) where P A is a finitely generated projective generator, and P can be generated by n elements, then sr(A) ≤ n· sr(B) − n + 1.