Fox Blocks FOX-EC690 6" 90 Degree Corner Blocks - 6 per Bundle - These Corner Blocks are used for ICF wall installations. The 90 Degree Corner Block typically makes up 15-20% 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.