GPIO Dual Edge connection is a board that leads the 40Pin GPIO pins of the ODROID (or any other board with 40pin GPIO) out of convenient use. It helps to connect peripherals horizontally and/or vertically. 

#1 pin is marked with a square shape pad on PCB
Virtually any small circuit module with a dual-row 2.54mm (0.1″)-center connector can be used.
Gold-plated 0.6mm square-pin terminations.
Quality 2-layer plated-through FR-4 board.