https://www.mcmaster.com/products/flat-head-binding-barrels-and-screws/
Flat Head Binding Barrels And Screws | McMaster-Carr
Choose from our selection of flat head binding barrels and screws in a wide range of styles and sizes. Same and Next Day Delivery.
flat headbindingbarrelsscrewsmcmaster
https://www.ncbi.nlm.nih.gov/Structure/pdb/1LKT
1LKT: CRYSTAL STRUCTURE OF THE HEAD-BINDING DOMAIN OF PHAGE P22 TAILSPIKE PROTEIN
crystal structureof thehead binding