For this question a manifold-with-boundary is a topological space which is connected, Hausdorff, and locally half-spaceupper-Euclidean. Every metrizable manifold-with-boundary has a collared boundary, as shown in "Locally flat imbeddings of topological manifolds", Morton Brown, 1962. Let $M$ be a non-metrizable manifold-with-boundary. Does $M$ have a collared boundary?