This particular detent kit for the Walvoil SD25 control valve is considered the "A" side spool positioner. The kit that I am assembling is detented in position 1 and spring return in the neutral position. The detent will allow the operator to push the handle and it will stay in position.
In some applications, this is needed so the operator does not have to stand at the control valve and push/pull the handle. When assembling the detent kit, it is very important to know the proper way to assemble. With this detent kit, in particular, knowing a few tricks beforehand will save you some headaches in the the end.