Fox Blocks FOX-TT600 6" Taper Top Block - 12 per Bundle - These Taper Top Blocks are used for ICF wall installations. The Taper Top Block typically makes up 1-2% of the ICF wall assembly on most residential and commercial jobs. This block has six strong, full-length, injection molded plastic ties made from Polypropylene (PP) regrind resin that are well marked with the words “Fox Blocks” located on both sides of the block.