LEGO Part Dark Blue Hinge Plate 1 x 4 Swivel Base with Same Color Hinge Plate 1 x 4 Swivel Top

Here we have a flat hinge – open it is a straight line 1 plate high and 4 studs long, but if you close it it is a 2×2 plate.  The hinge allows it to have any degree opening between 0-180 degrees, however because of the LEGO stud arrangements some angles might not “click in”.   I see this used a lot in buildings to open walls, but can also be used on spaceships to get the wings to move or any other way you want.

Lego Part Number: 6135593