You have to place it under the leg on the ladder which is on the lower side of the roof.
How to level a ladder on a sloped roof.
Ladders should not be used on a suitable surface where the side slope is greater than 16 or the back slope is greater than 6 unless the manufacturer states otherwise see image below.
Essentially this involves using rope cable or a ladder lashing kit to tie the rope to a secure point in order to prevent it from slipping or falling as you climb up.
If you need to use a ladder on a steep shingle roof you need a pivit ladder tool.
It requires to drill into the roof to fix it.
It s one kind of metal tool that works as a stopper for the base of the ladder.
Use a sturdy extension ladder that extends at least 3 feet above the eaves to climb onto the roof and secure the bottom to the foundation and the top to the eaves or fascia so it doesn t move.
What this will do is elevate the leg up to the same level as the other one.
Set up the ladder at the correct angle which should be 1 metre out for every 4 metres up or 75.
So your ladder will not be slanted anymore.
The pivit ladder leveling boxes are lined in rubber so that you a have traction to shingled roofs and provides some protection to the shingles.
Dig away high spots and fill in low spots with the dirt taken from high spots.
This tool will give you a sturdy and level base to place your ladder on slanted ground.
Extend the ladder and lean it up against the building wall.
Dig the ground with a shovel to make it as level as possible.
As a result it ll create a flat surface to the roof for the ladder to set up.
Lashing your ladder although not a perfect solution one of the fastest and easiest methods of securing a ladder for a slope is to lash it.
Step 2 lay a 12 inch square board over the leveled area to provide extra stability for the ladder legs.
You have to place the pivot tool under the feet of the ladder which is on the lower side of the surface or slope roof.