To place Hydrailic Objects upon AutoCAD Objects or lines, turn on AutoCAD Osnap and use its various specific snaps as you would for any new placements.

Caution: When near to any Hydraulic Objects, the Hydraulic Snap should be turned OFF, as it may cause placements to snap to the nearest Hydraulic Object, instead of to the AutoCAD Object of line.

A bit of practice, or during use, you will soon become familiar with how to use these 2 snaps to your best advantage. Experiment with using these snaps and you will soon get to know when to turn which snap on or off.