The newest craze sweeping un-carpeted steps everywhere, stair treads—like this set of four from Pottery Barn—let you feel at ease walking up and down wooden, stone or other slick-surface staircases.

DEAR TIM: I need to build some simple outdoor steps to replace ones that fell apart and rotted (even though they were made with treated lumber). I’m fairly handy and have a decent grasp of the math ...