Panels can be installed with a U-channel or clips.  Various sizes, from a full length panel to just  knee wall or seat are options.  

Shower Panel Set in U-channel
Shower Panel Set in U-channel
Shower Panel Set with U-Channel
Shower Panel Set with U-Channel
Oversized Panel set with U-Channel
Oversized Panel set with U-Channel

Has a Header to support the top

Panel with bench cut out
Panel with bench cut out
Side panels in U-channel
Side panels in U-channel
Panels with clips
Panels with clips
Panel set in U-channel
Panel set in U-channel
Full length panel in U-channel
Full length panel in U-channel
Full length panel in U-channel
Full length panel in U-channel