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Buckingham Lockjack
(a.k.a. Lockjack Twin)

Front Rear Rear: Open for Rigging
Front Rear Rear: Open for Rigging
Left Right Right: Open for Rigging
Left Right Right: Open for Rigging

Technical Details

I bought my Lockjack newfrom GearMerchant on eBay in July, 2005.

The Lockjack consists of an aircraft aluminum body, a 13 mm. black support line, and an 11 mm. orange control line. The description is somewhat complicated since most of the pieces are irregular. The body consists of a four-piece 54 mm. long, 58.4 mm. diameter cylinder with three smaller cylinders bolted onto its periphery. When closed, the main cylinder has a central rope groove cut in its circumference. The support line rides in this groove. A vertical hole on the right admits the climbing line, while a hole on the left admits the control line. A 33 mm. deep, 30 mm. diameter hole in the left side intersects the control line hole, and admits a knot in the control line. Naturally, there are a number of associated bolts and pins.

The main cylinder consists of four pieces: two 44.5 mm. pieces resembling semicircular cylinders, a 5 mm. thick round disc functioning as an end cap on the right side, and a 5 mm. annular disc functioning as an end cap on the left. The end caps are bolted to the first semicircular cylinder (hereafter called block 1)with two 5 mm., countersunk hex-socket screws each. Block 1 has vertical grooves milled in its flat face. These form half of the vertical holes mentioned previously. It also has horizontal grooves milled in its top that intersect the vertical grooves. When one loads the Lockjack, the climbing rope and control line lie in these grooves. The left side of the block has a semicircular cutout that forms half of the 30 mm. hole mentioned earlier. There is a 5 mm. tapped hole that passes horizontally through the bottom center of Block 1. An Allen screw in this hole allows one to adjust the fit of Block 2 (as I will call the second semicircular cylinder). Finally, a 40 mm. long, 12 mm. diameter aluminum cylinder with a U-shaped cutout is bolted to the back of Block 1 with two socket-head cap screws. The groove faces inward, and the support line runs through this groove. The fit is firm, but loose enough to allow moving the support line when one needs to open the Lockjack.

Block 2 has a circumferential groove, two internal vertical grooves and a 30 mm. cutout similar to those on Block 1. A small (4 mm.) hole passes through the block near its top, parallel to the cylinder axis. The right end is drilled out and tapped for a knurled 6 mm. screw that passes through the right cover plate when the Lockjack is closed, securing it together. A 4 mm. pin protrudes from the left side, and engages an internal slot in the left (annular) cover plate. A a 40 mm. long, 16 mm. diameter aluminum cylinder with a U-shaped cutout is bolted near the top of Block 2 with two socket-head cap screws. Like its analog on Block 1, its groove faces inward, and the support line runs through this groove. The fit in this cylinder is loose. A second cylinder (40 mm. long, 12 mm. diameter, stainless steel) is bolted just below the horizontal center plane. There are holes above and below this cylinder that pass from the circumferential groove to the central cutout. The support line enters the Lockjack through the groove in the open cylinder of Block 2, passes circumferentially over and down through the cylinder on Block 1, then under the body and through the hole below the stainless steel cylinder. From there it passes out through the hole above the stainless cylinder and finally down between that cylinder and block 2. The fit under the stainless cylinder clamps the support line in position.

The support line extends about 600 mm. below the body and ends in a tied carabiner loop. The control line is about 900 mm. between loops. The lower loop is a taped loop formed around the support line, and will not support weight. The upper loop is tied to accept a second carabiner. The control line as several overhand knots, one of which fits inside the 30 mm. cutout in the body of the Lockjack.

My Lockjack has a sticker on the right side that reads "Hersteller," "H. Kowalewski," "Rahden - Germany," "Lockjack," "T1," and "CE0299." A sticker on the other end has two up-pointing arrows and the word "Top." Block 2 has the numbers "00 104 0020" stamped in the periphery. Each of the six cap screws holding the cylinders on is marked "UV," "42," and"80."


I'm not Tarzan, so I hope that a real Tarzan will use their own web site to explain how to use the Lockjack in arboreal pursuits. The eBay auction description provided the following information:

Ascend, work, descend without changing rigging. This friction device is designed to perform a number of functions without adjustment. Your own weight on the support line rotates the unit, pinching the rope, and activating the brake. Since it has no moving parts to freeze or bind, it works in all weather conditions. Because of the rigging, the Lockjack advances itself no need to move your friction hitch up as you climb. To descend, pull the control line which straightens the Lockjack allowing line to pass through the unit. Descending is smooth and creates less wear on your climbing line than a friction hitch. With the self-advancing Lockjack, limb walking is safer as you take up slack with one hand upon your return.

This system includes: The Lockjack (constructed of hard coat anodized aircraft-grade aluminum), Black Support line and Orange Control line.

Use with two carabiners (not included).

Surfing the web didn't provide much information beyond the instruction manual. I learned that the Lockjack should be used with "1/2-inch, 12 or 16-strand climbing lines." One site implied that there were two versions (Sport & Twin) but did not elaborate (later I learned that this one is the Twin). Eventually I acquired a Lockjack Sport on eBay, and the seller provided more information on each. I placed the information on the Lockjack Sport page.