When glass panes (and metal bars) are attached to a block on only one side, the hit-box at the unattached edge extends some way beyond the rendered pane.

What I expected to happen was...:
When trying to attach another pane to the free edge, I expected to be able to click on the edge of the rendered pane.

What actually happened was...:
Because the hit-box extends past the rendered pane, I often end up attaching the next pane to the side of the existing pane, making a corner. This is particularly the case in the Nether or other dark environment where the hit-boxes are difficult to see.

Steps to Reproduce:
1. Place any solid block.
2. Attach a glass pane or metal bars to one side of the block.
3. Look at the hit-box.

I tried to produce a screen-shot showing the problem but the hit-box isn't shown in the screen-shot.