Contact of a thin free boundary with a fixed one in the Signorini problem

The Signorini problem is studied near a fixed boundary where the solution is “clamped down” or “glued”. It is shown that, in general, the solutions are at least $C^{1/2}$ regular and that this regularity is sharp. Near the actual points of contact of the free boundary with the fixed one, the blowup solutions are shown to have homogeneity $\kappa\geq3/2$, while at the noncontact points the homogeneity must take one of the values: $1/2,3/2,\dots,m-1/2,\ldots$