Threads, Fasteners & Springs — Double (and multiple-start) threads consist of two or more parallel helical ridges running side by side, increasing lead for faster linear advance per turn.

Introduction / Context:
Multiple-start threads (double, triple, etc.) feature more than one helical ridge on the same cylinder. They are used where quick engagement or rapid linear motion per rotation is desired, such as jar lids or quick-advance mechanisms.

Given Data / Assumptions:

• Two or more starts exist, equally spaced around the circumference.
• Pitch is the axial distance between adjacent threads of the same start.
• Lead equals pitch * number_of_starts.

Concept / Approach:
Adding starts increases lead without changing flank angles or basic form. This yields faster axial movement per turn at the cost of lower mechanical advantage and potentially reduced self-locking.

Step-by-Step Solution:
1) Identify the number of starts by tracing one ridge.2) Measure pitch on the same start.3) Compute lead = pitch * starts; confirm faster advance.4) Conclude the statement is correct.

Verification / Alternative check:
Mark one point on the ridge and rotate 360 degrees; observe axial shift equal to the lead (larger than pitch for multi-start).

Why Other Options Are Wrong:
One ridge with double height is not a double-start; multi-start increases, not halves, lead; knurls are surface textures, not threads.

Common Pitfalls:
Confusing pitch with lead; counting adjacent flanks from different starts as “pitch.”

Final Answer:
Correct