They built the tow and release mechanism for testing a space ship
on the taxi way

http://www.willswing.com/news.asp?newsSeek=745

Wills Wing was recently contracted with by Scaled Composites to
design and manufacture a tow and release system with a high working load for the
tow taxi testing of Virgin Galactic's SpaceShip Two.

In response to a few questions from me, Mike Meier replies:

We were towing it forward, in the normal direction, but in the
photo posted on the new item, the tow line has already been released, and the
spaceship is "coasting." None of the photos that Virgin Galactic posted on the
Flickr page actually show the spaceship under tow with the towing vehicle also
in the frame, although there are some that show the spaceship under tow. The
only difference you can see between under tow and off tow is that the orange
cone, which houses the release (to protect the spaceship from damage on snap
back) is stretched out horizontal if the spaceship is under tow.

The vehicle at the far right of the photo posted with the news item is a chase
vehicle - you can see a second chase vehicle on the far side of the space ship,
just visible underneath.

The spaceship is configured with wheels on the main landing gear and a skid on
the nose - the smoke in the photo is from the skid.

I'm sure there are others that could have made a suitable device, but there were
some technical issues involved in the testing that we have had some experience
with - high speed vehicle test operation on a runway, aircraft towing, release
system design.

Tow Taxi: A normal part of any aircraft development and testing program is a
series of tests known as "taxi tests." Before you attempt to take off or land in
new aircraft design, you want to first establish it's handling characteristics
on the runway at various speeds. SpaceShip Two is launched from a mother ship,
so takeoff isn't a consideration, but it lands as a glider, so handling and
braking on the runway are important things to test before the first actual
landing.