Timber hitches are used to secure a line to logs, planks, or other _______________________________________ objects.

Timber hitches are specifically designed for securing lines to objects that have a cylindrical shape, such as logs. This type of hitch is particularly effective because it creates a strong binding around the smooth, rounded surface of a cylindrical object, allowing for a secure hold even under tension. The nature of the timber hitch allows it to adjust to the shape of the log or similar object, making it less likely to slip compared to other knots.

While flat objects (like planks) or curved shapes could potentially be secured with various types of knots, the timber hitch excels specifically in the context of cylindrical forms due to its design and intended use. Therefore, identifying cylindrical objects as the correct choice aligns perfectly with its primary function.