If an LCD is subjected to physical shock, this could cause one or more TAB connections to fail inside the display. This failure is often caused by horizontally flexing the chassis (e.g. while wall-mounting or transporting a display face up/down) or simple failure of the adhesive holding the TAB against the glass. TAB faults require replacement of the LCD module itself. If these connections were to fail, the effect would be that an entire row or column of pixels would fail to activate. This causes a horizontal or vertical black line to appear on the display while the rest of the display would appear normal. The horizontal failure runs from edge-to-edge; the vertical failure runs from top-to-bottom.