Attachment locations are shown in a popup text box at the top center. When dragging a point, line, circle, etc over tools or intersections, a text box will popup near the top of the screen each time you pause while dragging. If more than one attachment option is available the text box will present multiple options.
To select an attachment point other than what’s currently highlighted in the text box, slightly wiggle your finger or quickly roll your finger left or right. This action will toggle through the choices. Let up on the point when the desired attachment point is highlighted.