Ivy needs very little grip. You may need to 'tack' a few tentrils onto
the wall when you first plant it, but it will 'catch' fairly quickly.
You could tie it up with a few nails. It developes suckers on the
stems where it connects to anything.

BUT, ivy can be very invasive and destructive. You can train it to
climb up, but it will want to spread on the ground, so you'll want to
keep an eye on that. Once it is rooted, it is very difficult to remove
- take my word. Also, watch that it doesn't grow in between your wood
slats or other openings in the wood. Eventually it will pull the wood
apart.

It will look pretty covering your wall, just keep an eye on it. Good
Luck, Laura