This hinged dashboard mount is compatible with many Garmin handheld GPS devices, such as eTrex 10/20/30, Oregon, Dakota, Colorado, GPSMAP, etc.
It is fixed to the dashboard with 3 self-tapping screws. The height of the hinge is parametrized in the SCAD file to allow fitting the mount to the desired opening angle and the space available on the dashboard. STL files of the base plate for hinge heights of 0mm, 5mm and 10mm are provided.
An M3x35mm bolt, an M3 nylock screw nut and 4 washers are needed for the axis of the hinge. The baseplate is mounted to the dashboard by means of 3 self-tapping screws.
Given that the clip part needs to have some flexibility, ABS is probably the best choice for printing.
See also my bar mount for the same type of GPS devices.
Update 2015-09-29: If you are looking for a dashboard mount for the older eTrex Cx/HCx Vista/Legend series of Garmin outdoor GPS devices, it is now available here.