Undercut anchors were so far seldom used in glass due to brittleness and the risk of subcritical crack growth. The use of tempered glass in combination with a special drilling-process and -geometry of the undercut holes now made it possible to develop a system that allows this method of fastening glass panes. In a parameter study of 3-D numerical tempering simulations with Narayanaswamy's structural relaxation model, the amount of residual stress in the area of the undercut hole was estimated. Temper stresses were compared to surface stresses in the “infinite” area that were measured by photoelastic methods. Pull-out tests and shear-off tests of anchors from annealed and tempered glass were performed and results compared to the numerical results. Both prove that a significant compression stress from tempering exists in the undercut area. Finally load bearing tests showed the performance of the system.