To trim without eating up weedwacker line, there are a few techniques and tips you can follow:

1. Adjust the cutting height: Most weedwackers allow you to adjust the cutting height. Set it to a higher level so that it trims the grass without hitting the patio or hard surfaces. This will reduce the chances of breaking off the line.

2. Use a trimmer head with a guard: Many weedwackers come with a guard or shield attachment that helps protect the line from hitting hard surfaces. Ensure that the guard is properly installed and positioned to provide maximum protection.

3. Angle the trimmer head: Tilt the weedwacker slightly towards the grass you want to trim, so that the line makes contact with the grass and not the patio. This requires some practice and control, but it can help prevent unnecessary line breakage.

4. Start with a higher speed setting: Higher speed settings on the weedwacker can help cut through thicker grass more efficiently. However, be cautious not to use excessive speed, as it can increase the chances of line breakage.

5. Avoid trimming against hard surfaces: Try to avoid trimming directly against hard surfaces like patios, walls, or fences. Instead, leave a small gap between the grass and the hard surface, and use a different tool (such as a trimmer with a blade attachment) to handle the areas near the patio.

6. Clear the area before trimming: Remove any debris, rocks, or other objects from the area you plan to trim. This will help prevent the line from getting tangled or breaking due to hitting objects other than grass.

7. Use a thicker line: Consider using a thicker and more durable line in your weedwacker. Thicker lines are less likely to break when encountering tougher grass or accidental contact with hard surfaces.

Remember, practice and patience are key to becoming more proficient with a weedwacker. It may take a few attempts to find the right technique and settings that work best for you and your specific trimming needs.