sdc
here’s an exapmle. Homeowner has 150K equity line with 100K balance. Homeowner refis into new eequity line product where the 100K is at a fixed rate and the unused 50K is still available at prime +/- whatever they qualify for.

Basically it allows someone with a heloc to have a fixed rate on the portion they have drawn while still preserving the right to draw the rest. I’m sure there are other uses but this is the obvious one to me.