Modern resistive chemical sensors include discontinuous nano/mesostructures. Sensing performances are then governed by the chemical nature of the nanostructure gap as well as by the sensor design at the nanogap scale. Various top-down, bottom-up and hybrid fabrication routes of discontinuous/nanogaped metal nano and mesostructures have been developed. These structures are assembled/organized on insulating surfaces for integration of resistor based devices for the specific sensing of chemicals in gaseous as well as in liquid media. Hydrogen sensing based on discontinuous/gaped palladium nano/mesostructures is a chosen case-study for the evaluation of various nano/mesogap fabrication methods.