Sentence:  Note, however, that when one cuts a 3-manifold along an incompressible torus, there is no canonical way to <WSD>cap off</WSD> the boundary components thus created, as is the case for spheres. For any toral boundary component, there are many ways to glue in a solid torus... . 
Meaning of the word marked with <WSD> tags:  To glue a relatively uncomplicated compact manifold to a manifold of the same dimension along (a component of the latter's boundary).