"Kanto" only refers to the external corner, architecturally speaking. If you're outside a box-shaped room, for example, all corners that you see are called "kanto". When inside the room, those corners are called "sulok" (internal corner).
"Ang mga alulod ay nasa apat na kanto ng bahay namin" = The downspouts are at the four corners of our house.
"Ang alaga kong aso ay mahilig matulog sa sulok ng kwarto ko." = My pet dog likes to sleep in a corner of my room.
"May tindahan sa kanto ng kalye namin" = There's a store at the corner of our street.
"Magkita tayo sa kanto mamayang alas singko" = Let's see each other at the corner later at 5 o' clock.