We report on a magneto-optical Kerr effect (MOKE) investigation of equilateral Fe triangles with continuous sides and with one and three notches forming a two-dimensional periodic array. The magnetization reversal was studied by regular longitudinal vector MOKE in specular geometry as well as in Bragg MOKE geometry, using the diffraction spots from the grating for hysteresis measurements. The measurements are compared with the results of micromagnetic simulation, which allows a detailed interpretation of the experimental data. We find that the remagnetization process in an external magnetic field strongly depends on the structure of the triangles (continuous or with one or three notches) and on the orientation of the triangles with respect to the magnetic field. The domain state in remanence is imaged using magnetic force microscopy.