A catheter adapted or high density mapping and/or ablation of tissue surface has a distal electrode matrix having a plurality of spines arranged in parallel configuration on which a multitude of electrodes are carried in a grid formation for providing uniformity and predictability in electrode placement on the tissue surface. The matrix can be dragged against the tissue surface upon deflection (and/or release of the deflection) of the catheter. The spines generally maintain their parallel configuration and the multitude of electrodes generally maintain their predetermined relative spacing in the grid formation as the matrix is dragged across the tissue surface in providing very high density mapping signals. The spines may have free distal ends, or distal ends that are joined to form loops for maintaining the spines in parallel configuration.