Allows adjustment in both up/down and rotation.
No real tools as such - snips to cut the cable tie - saw to cut the tube if you do not have an off cut laying around - a file to put a semi circle shaped cut out in the back of the pipe.
Step 1: Gather
1 - piece of tube - thin walled and about the same size as your seat post - length should be just short enough to let ya put the light on and off the bracket (if removable) - on a small note, do not make the tube too long or you will bust your light if you dump your uni.
1 - cable tie.