"There was a synagogue of Jews from Rome that was open to a room with a corpse and the Cohanim could not enter the synagogue to pray. They went and told Rava. He told them to lift up the ark and put it between the two rooms because the ark is a wooden utensil that is made to stay in one place and therefore does not become TAMAY (ritually impure) and can be a partition that the TUMAH will not pass through. The other Rabbis told Rava that sometimes the ark is carried around with the Torah Scroll on it. Rava then replied to the Cohanim that he has no solution (and must pray somewhere else)."

There are several categories of things which are TAMAY. None of them have the capability of causing the TUMAH to pass to something else unless it is touched or carried - except one*. A corpse or a piece of a corpse is TAMAY and can transfer its TUMAH throughout a house and into the next house as long as they are under one roof. If they are under one roof but in separate rooms, if there is a window between them as big as a hand-breadth, so the two rooms are filled with TUMAH and a Jew who is a COHEN is forbidden to enter either room. One way around the problem is to plug up the window. Then the Cohen can enter the room without the corpse. However not every plug will work. For instance, plugging it with a handkerchief or pieces of bread will not work.

Another way around it is to cover the window with a utensil - but the utensil must be incapable of becoming TAMAY. There are rules to these things. One rule is that anything which is sometimes empty and sometimes full that can be moved only when empty - is not able to be TAMAY. The example might be a portable bath-tub that when filled is too heavy to move.

Rava thought the ark of the synagogue was never moved when the Torah Scroll was on it. Therefore he concluded that the ark could not become TAMAY and could be placed next to the window between the rooms and block the hole. The other Rabbis informed him that he was incorrect in his assumption since the ark was sometimes moved when "full". Rava switched his opinion and told the Cohanim that he had no solution to their problem.

The truth is that if we had more information about the size and placement of the window between the rooms and if we had materials on hand to plug it up, we could succeed in fixing up the place for the Cohanim to pray. However, the story related by the gemorrah should be understood as I explained above.

* I should mention that there are cases of Zaraas that transfer TUMAH under one roof. I have reasons for not discussing that point now.