The chart key for the 3-st right slanting dec is missing--it is k3tog on RS, p3tog on WS rows it appears here on WS rows 4 and 8 of Shower Stitch. In addition the key for the 3-st left slanting dec should read sk2p on RS, p3tog-tbl (through back loops) on WS. Thus:

Chart Row 4 reads left to right: P3tog-tbl, yo, p1, yo, p4, yo, p1, yo, p3tog.
Chart Row 8: P2, yo, p1, yo, p3tog, p3tog-tbl, yo, p1, yo, p2.

Shower Stitch is not the easiest lace pattern to work as there are yo and decs on both RS and WS rows. But, it has a very striking appearance and is very satisfying once you get the hang of it. Pay careful attention to RS and WS rows. The pattern appears written out on p236 of Barbara G. Walker’s A Treasury of Knitting Patterns with Walker’s suggestion for an alternative method to p3tog-tbl for 3-st left slanting dec.