Park Tool Cable Stretcher BT-2

My Experience with the Fourth Hand

Assuming you don't have DI2 electronic shifting, your bike probably has cables. Adjusting, or installing new cables with the Park Tool 4th hand makes a complicated job super easy.  It is called the 4th hand because it is like having an extra person help you.  When I worked at a bike shop, we had one of these and it really sped the tune up process along.  I haven't invested in one myself, but it is on my list of things to get when I have some extra cash kicking around.  

Function

When you need to cut or adjust your cable, you have to let go of the cable itself.  That often results in dropping the cable and having to start all over, or having to do some sort of contortionist move to keep everything in balance.  If you are like me, repairs are frustrating enough without having cables escaping from you.  Here is a video from YouTube to show how it works.

Durability

If you wear one of these out, you must be doing tune ups all day everyday.  Our tool at the shop was years old and still functioned just like it was new.  That is the Park Tool difference.  I have gotten a few knock off tools in the past.  They last for a while but they usually break.  This is one that I would suggest investing in the Park Tool version.  If you are the type to take good care of your tools, you could make this last a lifetime.