How to check for an ulcer on elder?

Check all over: More detail as to what else afflicts this person would be helpful but in general look at all the skin especially where bones are just under the skin, heels, ankles, knees, pelvis , elbows, shoulders, ribs, along the spine, skin folds, and between the toes (especially in a diabetic) basically everywhere. Don't just look for open areas but for blisters and red, purple and dark areas.