Disclosed is a compression-based fastening device that is suitable for use with threaded fiberglass reinforced 
polymer (FRP) rod. FRP rod is often desirable due to certain favorable characteristics relative to metallic rods. Threaded FRP rod, however, has been somewhat unsatisfactory to date owing to the 
weakness of its thread structure. The herein disclosed device makes a threaded connection to a threaded FRP rod with an 
ultimate tensile strength that is several times greater than previously has been achieved with FRP rod, thereby effectively enabling FRP rod to be used in place of threaded steel rod. The preferred device includes a 
barrel with a tapered interior and a jaw 
assembly with a tapered exterior and internal threads. The jaw 
assembly's interior thread's engage the threaded FRP rod and the jaw 
assembly's tapered exterior slidably engages the 
barrel's tapered interior. As such, tightening the jaw assembly onto the threaded RFP rod also pulls the jaw assembly into the 
barrel's tapered interior so as to compress the jaw assembly against the threaded RFP rod and enhance the tensile strength of the threaded connection. Numerous embodiments are possible in terms of the configuration of the barrel, the jaw assembly, and the structure (e.g. an integral or separable nut) used to apply a tightening torque to the jaw assembly.