Summary: for me -- a piece of 19mm allen wrench silver soldered into a 19mm socket. The advantage of this tool is that I can use my 1/2 drive torque wrench to properly tighten the front axle. Another clever idea (from Will Hoctor) is to take a standard sized 5/8 sparkplug wrench (which happens to have a 19mm flange on one end) and insert an extension into the socket backwards (
Image Dimensions: 250 x 129
Image originally found here.