"Chock a block" is a commonly used phrase that refers to a situation where something is completely full or congested. There are several suitable synonyms that one can use to convey the same message. You can use phrases such as crammed, jam-packed, full, teeming, or brimming to describe a situation where there's no room to spare. Other substitutes such as overcrowded, packed, stuffed, or overfilled can also be used to describe something that is filled to capacity. Whether you are writing an article, or simply trying to describe a scene, using different synonyms for "chock a block" can add variety and interest to your narrative.