Work = force x distance (displacement) or the change in Kinetic energy
Carrying a box down a corridor has no external force acting on the box and therefore no work is being done.
Pushing against a locked door doesn't displace the door, so no work is being done.
Suspending a heavy weight with a strong chain requires, no force and actually prevents a force from acting on the chain.
Pulling a trailer up a hill on the other hand requires a person to apply a force to the trailer and displace it up the hill and therefore it requires work.