Image courtesy of knifecenter.com.

Leather faced "paddle strops" are popular tools for honing knife blades. A conventional paddle strop consists of a leather strip glued onto one or both sides of a wooden or synthetic backer board.

The unique design of the Boker Spann tool takes the paddle strop concept to another level. I recently stumbled across the Spann strop quite by accident and quickly concluded that it was worth adding to my knife sharpening tool set. I was not disappointed, for the Spann strop has a design and function feature not found on normal paddle strops.

Here is a summary of features:

• Steel frame, including spacer rods, end plates and tension adjustment plate
• Double sided leather hone strap, smooth finish on one side, rough finish on the other
• Strap tension is adjustable (this is the unique feature)
• Strop length 7-1/8", width 1-5/8"; overall length 13-3/8"

The tension-adjustable frame starts with two spacer rods. These are anchored to a flange at the front of the handle. The rods run through holes in a tension adjustment plate at the back (handle) end of the strop and extend to to an end plate at the front of the strop.

A screw protrudes from the front of the handle and threads through the tension adjustment plate. Turning the handle clockwise draws the adjustment plate toward the handle, which tightens the leather strop. Thus, the tension of the strop can be tuned, depending on what works best for a particular blade that is being sharpened. This is a feature unparalleled on any other stropping tool I have encountered.

I back the tension screw off a bit when I am through using the strop. It seems prudent to not store the tool with a lot of tension on the leather.

The one small glitch I found in the frame design is that the rods are not solidly attached to the front plate. Rather, the ends of the rods rest in dimples in that plate, which means that they can slip out of position if the strop tension is loosened enough. I solved this by applying a drop of super glue to the front end of each of the rods.

A bare leather strop does not do much when it comes to putting a keen edge on a knife blade. The game changes when the leather is coated with stropping compound.

There are four common grits of stropping compound, which are readily identified by color. Black compound has the most coarse grit, followed by white (medium grit), green (fine grit) and red (very fine - really a polishing compound). The black compound, plus the white or green, are the ones most commonly used for two-stage stropping.

Stropping compounds. Illustration courtesy of StropMan.com.

I have black and green compounds on hand, so I prepped my Spann strop by working a thin coat of black compound onto the rough side of the leather and applying the green compound to the smooth side.

To test the tool, I did a touchup sharpening on the four pocket knives that I carry and use the most. None of the blades were really dull, but none were as sharp as they could be.

Using only the strop, I worked each of the blades on these two or three blade pocket knives, first on the black side of the strop, taking a half dozen alternating strokes on each side of each blade. Then I did the same on the green side. All of the blades came out at what I call extremely sharp condition, what is often called "shaving sharp." Verdict: the Spann strop, properly prepped for use, works very well.

Incidentally, the StropMan.com (http://stropman.com) website is a good place to shop for stropping compound. They sell all four grits shown and explained above and even give a price break if you order more than one stick or type of compound. StropMan also makes and sells several models of conventional paddle strops.

The knives I used to test the strop all had flat ground blades, with micro edge bevels. However, it will also work well on any other type of blade grind.

Given that the strop tension is adjustable, I believe that the Spann tool would really shine at honing convex ground blades. I have not yet tried this, because the one convex ground knife I have at the moment does not need any work and I could not bring myself to purposely dull the edge for testing purposes. A paddle or bench strop is an essential tool for sharpening convex ground blades. (See Sharpening Convex Ground Knives for more information.)

I happened across the Spann strop while browsing a special Boker products sale on the Knife Center website. The 2017 MSRP is $49.95 and Knife Center sells it for $37.95. I judge this to be a reasonable price for a well designed, quality product.