cap off

verb2

1. •
   To finish by making one last addition.
2. •
   To glue a relatively uncomplicated compact manifold to a manifold of the same dimension along (a component of the latter's boundary).

   • Let X be an acyclic 2-complex and M an abstract regular neighborhood of X; ∂M_0=S², so cap off to get a homology 3-sphere M³. — 1997