B757 Flight Attendant reports that the shorter B777 galley carts; which are sometimes boarded; are not compatible with the B757/767 galley compartments; while the taller B777 carts are compatible.

Narrative

We took a delay of 30 mins while three B777 carts were changed out for the taller 777 carts. This was so the cart doors would be secured by the quarter turns. The carts were full of metal racks of food items and supplies (soft drinks). I ordered the exchange of carts because a year ago I talked to Mr. X with FAA about the problem of 757 places being repeatedly boarded with these shorter carts with no secondary restraint for the doors. These carts have a metal lever with what they call a 3 point locking system. The lever is loose and can be lifted with the little finger. He told me all carts need a secondary restraint and he would look into the matter. He said he knows there were tall 777 carts and short carts but he has only approved the taller carts. For months afterwards I noticed only the tall carts were being boarded. Mr. Y told me the company had 2 years to change the quarter turns to longer quarter turns on the 757's but they hadn't done it yet. This was after I had spoken with Mr. X . So Mr. Y said if the food from the shorter boarded carts couldn't be exchanged for taller carts then the food should be put in other existing carts and the shorter carts that couldn't be closed by the quarter turns; needed to be taped up so they couldn't be used in flight. One flight they found taller carts and the exchange was made. When we arrived that night Mr. Z met our flight and said we had been approved to use these shorter 777 carts because of the 3-point locking system. My concern is why is there not a secondary independent restraint securing the cart doors on the 757 planes we have? The 3-point system is excellent as long as the plane does not have a hard landing or crashes. It wouldn't take much for that loose metal lever securing the 3 points to pop up and all the contents come flying out landing on the floor and making doors L and R unusable. Not only that but the poor flight attendant sitting in front of the food cart with the metal racks would be severely injured or worse. Please look into this matter. It only takes one accident to prove my point. On even one of these carts latching shut 'falsely' by a flight attendant hurrying to reach his/her jumpseat and then a hard landing or something to cause the contents to come streaming out.