 Image charges in a right-angle conducting wedge

For conducting sheets $y=\pm x$ at common zero potential and a charge in $y>|x|$, successive reflections give two negative images and one positive double-reflection image. On the bisector, the negative images lie at $(\pm y,0)$ and the positive image at $(0,-y)$. Summing their fields gives the displayed downward force. Image forces exclude the real charge's self-field; replacing the induced charge by images does not make the images physical particles.