I need some help with handle.
The following passage was written by Joseph Wolf, a German artist who specialized in natural history illustration.
I used to go to see Livingstone at Sloane Street; and he would propose subjects; but there was no handle to what he said. He had a thing in his mind that couldn't be illustrated. I couldn't make pictures of what he thought would be the best subjects. I didn't feel the inspiration to work with Livingstone.
At the time, he was drawing illustrations for David Livingstone. Livingstone described scenes he saw in Africa with words, Wolf was trying to draw from it. I can feel Wolf was not happy with Livingstone, but I have no idea what 'handle' means here. Some help would be great!