A while back a topic was about sponges.Most responded about couch cushions or other square type of sponges.
ABC has a sponge approximately 18" wide and around 3’ long and 4" thick.It also has a built up end that the shingles catch on stopping them from sliding down the roof vertically.
I used them but they (IMO) held under a bundle and when it was hot the shingles would roll over the stopping area.
These wedges are the sh**.I use them up to a 10/12 with ease.I have used them on 11/12 and 12/12 but they would have to be used vertically.
These sponges will hold 2 bundles at a time.They are cut with 2 angles,1st up to a 8/12 and the other for steeper pitch.
The sponge shown is new and the older 1 above it is about 2 months old.I am paying $18 per sponge.It is money well spent IMO.