Petzl highly recommends that the TIBLOC is used with round profile carabiners, but they suggest the hole on the S'MD carabiner (NOT round C-section) is for loss prevention of a TIBLOC. What
Petzl Tibloc - Everything you need to know — Alpine Savvy
Petzl TIBLOC Ascender
First Look Review: New Petzl Tibloc 2 - Black Sheep Adventure Sports
Progression with a taut rope using a TIBLOC - Petzl USA
Appendix 3: Detail of installation on one rope with two ascenders - Petzl Netherlands
Petzl Tibloc - Everything you need to know — Alpine Savvy