Frequent readers of this column are cognizant of the Vertically Oriented Strike Indicator, for which its acronym VOSI has become well-established and even published in books.

Call it the fly-rodders' popping cork. At least, that was the intention.

In the early '90s, I decided to "match the commie hatch" of plastic under a popping cork. I borrowed on a concept originated by Louisiana fly fishing pioneer Pete Cooper Jr., by which his famous Perch Float Popper is made from a styrofoam cigar float cut in half.

I simply took the half perch float and carved out a concave face with a Dremel cone. The face end slides up the leader toward the fly line. At the appropriate distance above the fly, the peg is stuck into the opposite side of the float.

When you pop the float, it not only makes a sound that attracts specks, but causes the suspended fly below to dance vertically. That simply infuriates the trout, since they are vertically challenged.

I'd just read a story about a fly angler in England who was banned from a river for using a cork when I was contacted by a writer about this technique. I jokingly told her that this was not a cork, but a "vertically oriented strike indicator."

Apparently, she took it serious — and the rest is history.

A few years later, my good friend Randy Leonpacher figured out that "half a perch float" also made a pretty good — and cheap — freshwater strike indicator. Instead of pointing the face of the VOSI toward the fly line, he pointed the narrow end toward the line.

Of course, I get questions all the time about vertically oriented strike indicators. I've picked the most popular to answer here.

Q. Why doesn't my VOSI make a popping sound when I strip fly line?

A. Several possibilities. In most cases, the problem lies with the leader. You need a light leader and a weighted fly to make it work.

Most of my leaders for marsh specks consist of a 4-foot butt section of 18-pound mono and a 3-foot tippet section made of 12-pound fluorocarbon. I use a double uni-knot to connect the mono and fluoro lines.

The VOSI goes on the tippet (fluoro) section, just below the joining knot. The combination of a high-density tippet and a weighted fly causes the VOSI to sit slightly below the water line. When stripped, it digs into the water, and that causes the popping sound.

If you're fishing choppy water, try a bigger VOSI. The standard version is made from a 1 ½-inch-long cigar float. Try one made from a 2-inch float.

If all that fails, try flicking the end of your fly rod instead of stripping line. This often works when the fly line has some wind-generated slack.

Q. I fish Lake Pontchartrain a lot. I've tried using various flies suspended under a VOSI, but with no success. What am I doing wrong?

A. I've observed over the years a few situations where a strike indicator doesn't work well, and one of those is clear water — which is characteristic of much of Pontchartrain.

I'd suggest using an intermediate sinking fly line instead of a floating line with a dropper setup.

Q. I was using a jitterbee under a VOSI for bluegill at one of the City Park ponds. Seems like the blues were aware of the float and wouldn't show interest in the fly unless I took the VOSI off.

A. Clear water could be a culprit, but I suspect it's one of two other possibilities.

First, sometimes bream are attracted to the VOSI itself — it looks like a big bug. If it gets strikes, replace your setup with a popping bug.

The second possibility is that they are float-sensitive. Sometimes even half a perch float is too big. For such cases, I've started making an even smaller version of the VOSI — a Mini-VOSI — one-fourth the size of the perch float.

Simply cut the float in half again. Don't bother making a concave face, as this is a freshwater application (the concave face only works for saltwater).

Q. I bought a pack of Comal floats, half-red and half-white. I cut each in half, and ended up with four red VOSIs and four white VOSIs. The white VOSIs are hard to see when fishing. What should I do with those?

A. Paint them a high-visibility color like orange or chartreuse with a permanent marker. Or you could use them to make Perch Float Poppers. Do an Internet search on "Perch Float Popper" and you'll find several how-to articles, including one in the Louisiana Sportsman archives in which I gave step-by-step instructions.

Q. A slit lengthwise in the VOSI would make it easy to take on and off, as opposed to having to cut off the fly and retie. But you advice against a slit. Why?

A. Ever saw the movie "The Blob"? A slit in foam is like the Blob, it just keeps growing. It doesn't take long before it grows so wide that the peg falls out, usually on a false cast. I had a buddy make VOSIs out of slit corks. He used up one bag of corks — eight VOSIs — in one trip.

If you have other questions about using VOSIs, shoot me an email at catch@laflyfish.com. Now is the time to prepare flies — and VOSIs — for what promises to be great fall and winter marsh fishing ahead.