Devices, assemblies, and methods for fitting and maintaining medical lines are shown and described. In one embodiment, a fitting system includes a housing having a spool and a removable upper cover to secure medical lines without obstructing flow. Other embodiments include a catheter assembly having a peripherally inserted central catheter and a housing fitting. Certain peripherally inserted central catheters include an inactive anchor. The result is devices and methods to improve medical line fitting, placement, advancement, and stability.