Two little tools to see if your Ultimaker XY guiding rods timing belts are correctly aligned according to the 'sliding blocks'
The optimum is that the timing belt of the X -rod has no Y component, so the 2 pullies and the 'sliding block' must be in the same Y-plane.
This should reduce mechanical stress in the system and gives a more balanced load for the belts/pulleys.
It can be difficult to see if the pulley is mounted straight above/below the rods.
The tool has a complexity/added value ratio of 1 (It can boost your Ultimaker performance with at least 0.000005%)
Place the rounded tool over the X rod and see if the underlying belt is not touching the legs (4 times, each corner once).
Place the right-angled tool over the Y belts and see if the underlying rod is not touching the legs (4 times)