An SL block is an octocube that can be used to build semi-interlocking structures called SL strands. The study uses context-free grammars to define languages of SL strands. Several grammars are devised to display the relation between string rewrite rules and SL block constructions. It is expected that with syntactic operations based on grammars, computer modeling tools can be developed to assist artistic creations by enabling transformations and form finding between high level abstractions and low level constructions.