I use the Peak Design Everyday phone case which has a neat little finger loop that keeps it secured to one's hand.
The loop folds entirely flat when not in use. Almost too well. It makes it difficult to slip my finger into it using just one hand.
So I printed this wedge shape to temporarily insert into the loop (overnight) to pre-stretch it, such that it leaves a 2mm gap that I can slip my fingernail into for single-handed deployment.
Version history
The author marked this model as their own original creation.