This tip comes from IFMGA Guide Karsten Delap. Connect with Karsten on his website and Instagram.

When top rope belaying with a Grigri or similar auto locking belay device, you may find you need extra friction when lowering. This could be due to lowering a heavy partner, skinny rope, slippery rope sheath, wet/icy rope, cold hands, gloves, or some combination of the above.

One crafty way to do this is to redirect the brake strand through a second locking carabiner clipped to your belay loop.

You can use a normal locking carabiner to do this, or the more specialized (and expensive, and strange looking) Petzl Freino carabiner, which has a secondary “braking spur” designed specifically for rope redirect and extra friction when belaying or rappelling a single rope strand.

Like with all lowering techniques, the effectiveness of this depends greatly on the variables mentioned above: rope diameter, how slippery the sheath is, if the rope is wet / icy, weight of your partner, etc. Practice in a controlled environment before you try it in the real world.

Karsten posted two nice photos on his Instagram, which pretty much sums it up.

Method 1 - SOME extra friction - brake strand redirected through the gold locking carabiner.

Method 2 - a LOT of extra friction, with the brake strand redirected through the locking carabiner AND passed back over the Grigri.