Align edges consists of parallel rails that the robot needs to stay on. These rails need to be adjustable to the width of the robot. In the mini arena scale, strips of velcro are used to hold the rails down.
The overall components are as follows. It is perhaps easiest to staple these together, screws can be used instead if necessary. 
- (A) 4x 15 x 300 x 300 mm (12 x 12 in) OSB sheets.
- (B) 2x 15 x 300 x 600 mm (12 x 24 in) OSB sheets.
- (C) 4x Rails (see below).
- (D) 4x 50 x 300 mm (2 x 12 in) velcro strips, loop side.
Each of the 4 rails is constructed as follows. These should be glued or stapled together. 
- (C1) 15 x 25 x 450 mm OSB strip.
- (C2) 15 x 25 x 350 mm OSB strip.
- (C3) 15 x 50 x 50 mm OSB square.
- (C4) 50 x 50 mm velcro square, hook side.