If a room, or area is very full of things or mortals, one can say that it is “chock-a-block”.
Here are the origins of the phrase. Many moons ago, in the 15th century, ships used chocks (calzos) or wedges to stop something from moving. These chocks or wedges “blocked” movement in the ship´s rigging (jarcia).
So, for ships, if something were “chock-a-block” it meant that the rigging was so tight that it could not move: there was no space for movement, that is, space for movement was blocked.
So, nowadays, if a room is so full of mortals and there is little space to move, it is “chock-a-block” (totalmente lleno de…). A room can also be so full of things that it is difficult to put more in it – the room is chock-a-block of things. Perhaps, on national holidays or special events the squares in Spain are chock-a-block with people.
Another similar expression is “chock-full” (lleno hasta los topes). Perhaps you have been to events where the locations were chock-a-block.
