The phrase "a safety line" is correct and usable in written English.
It can be used in contexts related to safety measures, such as in construction, outdoor activities, or emergency situations.
Example: "Before starting the climb, make sure to secure yourself with a safety line to prevent any falls."
Alternatives: "a safety rope" or "a safety tether."
You are attached to a safety line, so there's no need to worry.
"Now it's just any person — I would try it if I had a safety line on".
Mr. Jara's harness was not attached to a safety line, a rarity, his brothers said yesterday in hushed tones.
After the vertigo-inducing climb, Ms. Smith secures a safety line to a flier's thick leather belt.
The guides hooked my harness onto a safety line attached to the tree but this did little to allay a wave of panic.
They followed a safety line to a spot where the remnants of a sightseeing helicopter were resting on the bottom of the Hudson, embedded among rocks, mud and the rotting, jagged pilings of a collapsed pier off the New Jersey shore.
Window washers are attached to the rope by a short safety line and a ratchet, which is too weak to stop the dead weight of a falling man until he has already plunged 100 feet or more.
No wonder: The water is over 12,000 feet deep, and its temperature a bone-chilling 28 F. I took clothes off to reveal a fiery red bathing suit underneath, and wrapped a tether safety line around my waist.
Since 2001, 3M has developed a "smart safety" line of respirators aimed at responders who do not normally use such equipment.
Smooth-sheathed nylon ropes were affixed to the rock face to make a continuous safety line, which climbers could ascend and descend very efficiently.
As well as its luxurious cabins in the Forest of Dean, Forest Holidays offers the chance to climb the mighty limestone Symonds Yat crag, then abseil back down to earth again – with instructors controlling a backup safety line.
