1. I can’t hear you clearly because the telephone connection is bad. I can’t make heads or tails of what you’re saying.
2. First Louise turned the book one way, then the other. She couldn’t make heads or tails of the picture she was looking at.

The head is the top or front of something, while the tail is the bottom or back. In use since the 1600s, the phrase make heads or tails of something means to understand it from beginning to end (top to bottom). The expression is usually used in the negative or in question form.