Front View: Closed	Rear View: Closed
Front View: Open for Rigging	Rear View: Open for Rigging

Technical Details

I acquired my NTR Grab from Andy in China in 2017.

My NTR is 69 mm. long, 114 mm. wide, 29 mm. high, and weighs 173 g. It consists of a movable lever and a fixed anvil sandwiched between two plates. The rear plate is a rounded American football-shaped stamping made from 3.9 mm. anodized aluminum. A round 14.9 mm. hole is cut in the top side of the plate, and a larger 25.7 by 27.2 mm. hole is cut in the bottom side. The front plate is pear-shaped and smaller, lacking the projection for the upper hole. The front plate pivots on the lever mounting pin, and a notch in the left side of the front plate provides clearance for the anvil mounting pin. The anvil and lever appear to be 13.3 mm. slices cut from an aluminum extrusion. The anvil is attached to the rear plate by a rivet and a split pin. The anvil itself is shaped like a low, wide isosceles triangle, with a cutout opposite the lever end. The lever is mounted on another rivet, but is free to rotate. A small spring forces the lever to the engaged position. A cutout on the rear side of the lever provides clearance for the spring.

The front plate is printed with "NTR," "EN353-2," "Ø11~12.6mm," " "EN358," "Ø12~12.6mm," and "CE1019." The inside of the rear plate has the "Sieg Heil" icon stamped between the hammer and anvil.

Comments

The following rope grabs are all variations of the same basic design:

Image	Rope Grab	Manufactured	Side Plates	Lever Locking Tab
	ISC Rocker	2006 (?)	3.9 mm. Anodized Aluminum	Yes
	NTR Rocker	2017 (?)	3.9 mm. Anodized Aluminum	Yes with forward fold
	Proverti AC080	4/2015	4.4 mm. Anodized Aluminum	Yes
	Proverti AC081	4/2015	2.5 mm Stainless Steel	Yes
	SAR Rocker	2012	3.9 mm. Anodized Aluminum	Yes
	Singing Rock Locker	1/2008	4.0 mm. Anodized Aluminum	Yes
	Troll Rocker, Version A	~2001	4.3 mm. Anodized Aluminum	No
	Troll Rocker, Version B	~2003	3.9 mm. Anodized Aluminum	Yes
	Vento (Венто) Rocker	~2019	3.9 mm. Anodized Aluminum	Yes
	Xinda Rocker	~2014	4.0 mm. Anodized Aluminum	Yes
	Vertical (Вертикаль) Rocker ver 0115	12/2021	4.0 mm. Anodized Aluminum	Yes with forward fold
	Yates Rocker	~2003	4.3 mm. Anodized Aluminum	Yes
	Z&W Rocker	~2019	4.0 mm. Anodized Aluminum	Yes with forward fold

Each of these is a compact, lightweight (except for the stainless steel Proverti AC081) fall arrest that can also be used as a ratchet when hauling loads over a pulley. They can all be used as rocker-arm ascenders, but that was not the original design intent for the Troll Rocker, the progenitor of the others in the chart.

These have no sharp teeth to cut the rope sheath. Some informal testing suggests that, lacking teeth, these can slide before engaging, but normally the slippage is less than a foot. The cases where I observed this were somewhat contrived (i.e., I held the grab in a specific position and carefully dropped the load straight down), and so I'm not too worried about the slippage. I would be far more concerned if they had sharp teeth and didn't slip at all.

The top hole is used for releasing or offloading a locked rocker by placing a carabiner in the hole and pulling toward the slack rope.

Except for the early Troll, each of these incorporates a lever lock. Troll added one to theirs before the others came out. The lever lock works, but one needs to be careful not to bump it so that it accidentally disengages. A carabiner in the upper hole can help prevent this. When the lever lock is disengaged, it blocks access to the upper hole.

The NTR, Vertical, and Z&W have a forward 90° bend at the top of their lever lock, making their locks much easier to operate than the others that rely on shallow rounded serrations.

Troll warns that using a rocker as a on soft or loose-sheathed ropes can cause the rope sheath to slip or tear. They also warn that rope conditions (water, ice, mud, dirt, etc) as well as rope diameter, manufacturer, etc. will affect device performance. These warning apply to all of these fall arrests.