An apparatus (100), including: a holder (102) configured to hold a rod, wherein the holder is configured to tilt about a pivot joint (120); and a pinching element (122) held in a fixed position relative to the holder and comprising a contact surface (124), in A distance (D1) between the contact surface and an interior surface (108) of the holder opposite the contact surface decreases as the holder tilts about the pivot joint toward a pinching configuration.