Burls, tree fungus
Lemon, grapefruit, palmetto or orange peel
Knuckles & knees
Old seat cushions
Roller coaster ride
Warped & scarred tables/benches/picnic tables
Buttons on a phone
Crusty bread or pizza crust
Cave or tunnels
bumpy, lumpy, knobby, uneven, rough, irregular, clumpy, coarse, pebbly, pocked, nubby, chunky, gnarled, hilly, scabby
Describing texture in a story creates intimacy between reader and character, and can even cause an emotional trigger for both. To anchor the reader in the scene, make sure comparisons and contrasts are clear and relatable, and within the scope of the narrator's life knowledge and experience.
A weak example:
I rooted through the cardboard barrel, sorting through the pumpkins. A squat one with a streak of green on one side caught my eye and I hoisted it up. This would make a perfect first jack-o-lantern for Sarah. I ran my hand over the smooth orange ridges, brushing away dust. Strange how nature could make something be both smooth and bumpy at the same time.
What's wrong with this example?
This one's tricky, because there's good description that creates recognition--as the character experiences the bumpy and smooth texture, so does the reader. However, while relating to the texture is the goal, we don't want to go so far that the reader ends up thinking about this oddity in nature and how it relates to the cosmos instead of what the character is experiencing (picking out a first pumpkin for his daughter to carve).
A strong example:
I held tight to the plastic handle above the cracked side window, trying to keep some part of me unbruised as Raymond's pickup bounced over driveway's bumper crop of ruts and potholes.
Why does this example work?
This one creates instant recognition--we've all travelled bumpy roads--without derailing the story.