Fox Blocks FOX-TB600 6" T Blocks - 6 per Bundle - These T Blocks are used for ICF wall installations. The T-Block (Short Leg) typically makes up 1-2% of the ICF wall assembly on most residential and commercial jobs. This block has eight strong, full-length, injection molded plastic ties made from Polypropylene (PP) regrind resin that are well marked with the words “Fox Blocks” located on all sides of the block.