In the Elbe Sandstone Mountains two-stranded Figure-8 knotted slings are commonly used as climbing protections. These protections are examined experimentally using 8 mm technical accessory cord in an artificial crack test rig. The resulting load-bearing capacity, in terms of the maximum force, is characterized for different friction linings, crack angles and crack widths. Based on the experimental results and an analytical model, it is demonstrated that for crack angles below 20° the required crack widths are less than the 1.5-fold rope diameter to effectively withstand typical forces encountered during a lead climber fall.