Chad Field put them ahead but Joe Alman was sent off before the break.
Gareth Chendlik levelled from the spot early in the second half and Lenny Farhall got Harrow’s winner late on.
The defeat left Bognor 15th in the table ahead of their bank holiday Monday trip to Horndean.
See pictures by Lyn Phillips and Trevor Staff on this page and the ones linked. Get all the Rocks news in the Bognor Observer and on this site duting week.
13. Lyn Phillips
Harrow Borough v Rocks, Isthmian south central Photo: Lyn Phillips and Trevor Staff
14. Trevor Staff
Harrow Borough v Rocks, Isthmian south central Photo: Lyn Phillips and Trevor Staff
15. Trevor Staff
Harrow Borough v Rocks, Isthmian south central Photo: Lyn Phillips and Trevor Staff
16. Trevor Staff
Harrow Borough v Rocks, Isthmian south central Photo: Lyn Phillips and Trevor Staff