Don Vandervort, Head Homeboy, has written more than 30 DIY home improvement books, been a segment host on HGTV, served as MSN.com's home improvement expert and written countless magazine articles.
Hardboard’s worst enemy is moisture. Immediately fill holes with a flexible, all-purpose filler such as pre-mixed bridging and patching compound, following all label directions. Sand the area smooth, and then paint it to match the rest of the siding.
For deep holes, build up the patch with several successive layers, allowing each to dry before applying the next.
