The grid technique is an experimental method for measuring the deformation in hot rolling. An AA3004 sample -fitted with an insert - was rolled in a single hot rolling pass at 400 oC. The insert was hand engraved with a 1x1 mm grid and the analysis of the image of the deformed grid enabled the calculation of the components of the deformation gradient tensor. In order to prevent relative motion between the insert and the work-piece, four steel pins were used; after the test no detachment was observed between insert and sample. The temperature was monitored during rolling using two embedded thermocouples, one close to the surface and the other on the centre-line of the slab. The commercial finite element (FE) code ABAQUS was used to build a threedimensional model of the rolling process. The recorded temperature was compared with the FE values evaluated after tuning the heat transfer coefficient. The FE model was run several times with different friction coefficients and the deformation gradient checked against the experimental measurement of the deformed grid in order to obtain the optimum friction coefficient. The experimentally determined deformation gradient and the measured temperature agreed well with the numerical values.