Recently, Manulescu, Ozsváth, Sarkar, Szábo, D. Thurston gave a combinatorial construction of the Heegaard-Floer homology of links based on the presentation of links by "grid diagrams." I will show how grid diagrams can be used to solve a problem in a different area, namely the determination of the singular locus of a Schubert variety. My talk is based on joint work with Alain Lascoux and Christophe Reutenauer (J. of Algebra, 2003).