When you cut me, you’ll get there faster, When I cut you, you’ll need a plaster. You say we are part of your eye, But speaking the truth, that’s a lie. What am I?

This clever riddle plays on the many meanings and common idioms associated with a simple geometric concept. The first clue, "When you cut me, you’ll get there faster," points to the phrase "cutting a corner." This idiom refers to taking a shortcut, whether literally in a physical race or figuratively by finding a quicker, often less thorough, way to complete a task. It implies efficiency, even if sometimes at the cost of precision.

The contrasting line, "When I cut you, you’ll need a plaster," refers to the physical nature of this object. A sharp edge, such as the intersection of two walls or a piece of furniture, can easily cause a scrape or a cut if one isn't careful. Bumping into such an angle often results in a minor injury that might indeed require a plaster or bandage.

Finally, the lines "You say we are part of your eye, But speaking the truth, that’s a lie," highlight another popular idiom. We often talk about seeing something "out of the corner of our eye," referring to our peripheral vision. However, anatomically, there isn't a specific "corner" that is a distinct part of the eye itself. Instead, it describes the outer or inner junction where the eyelids meet, illustrating how language can create descriptive but not always literal terms for our anatomy. This versatility makes the word a perfect fit for such a riddle.