The flow of fabric reinforced polymer sheets during sheet-forming processes is dominated by shearing along fibre directions. The goal of this work is to develop models which describe the rheological behaviour of commercially available fabric reinforced thermoplastic sheets. Isotropic and anisotropic models which feature viscous and viscoelastic behaviour and which are suitable for describing processes involving large deformations are developed. Kinematic constraints of fibre inextensibility are used to represent the extremely high resistance to deformation in the reinforcement directions. The suitability of this approach for modelling planar hows of fabric reinforced polymer melts is established by the interpretation of experiments involving two commercially available material systems using a specially developed picture-frame shearing experiment. Shearing flow is imposed on pre-consolidated laminates via a four bar linkage which is loaded by a test machine. The picture-frame apparatus is housed in an environmental chamber and experiments are reported at temperatures in the materials processing range. Force versus displacement data is available for experiments conducted at different actuator displacement rates, and stress relaxation behaviour is also considered. Methods are presented for interpreting the response of two glass fabric reinforced PA-12 materials in terms of a number of continuum models, including Newtonian models, power law viscous models and shear rate dependent Kelvin type material models, all of which feature inextensible fibre directions.