1–
: 1c+4c set, cast to middle positions (2c+3c step to end) ; 1c&4c ½ Fig8 round end C (2,1x,4x,3)
9–
: 1M+4M and 1W+4W cross NHJ, (W under men's arch), turn cnr ¾ with 'free' hand ; 1c facing 4c change places NHJ (arch going up), turn cnr as before
17–
: Repeat (Men's arch ; arch going up)
25–
: 1c+4c ½ R&L ; turn P RH

{{explanation}}
Note that both times the couple moving UP makes the arch.