Abstract: A carton glue monitoring system includes a conveyor moving a plurality of cartons in a first direction. An encoder provides pulses at a rate proportional to conveyor line speed. A glue applicator applies a glue strip having a fluorescent material added thereto to the cartons on the conveyor. A glue check station includes a UV source for illuminating the fluorescent material in the glue and a UV sensor for sensing the fluorescent material. The glue station further includes a glue skip detector and an excess glue detector for generating a glue flag and for holding the glue flag until the carton exits the glue station. A glue shift register includes Y registers and is connected to the UV sensor and the encoder for shifting the glue flag in the Y registers. Y is proportional to the encoder rate and a distance between the rejection marking device and the glue station exit minus the carton length.