here is some text from greenglides.
So many people ask us how a glide works that maybe it is time to put a detailed explanation up:
As to the vac restriction angle, it is probably the hardest thing for most guys (and girls) to get their heads around and this is how I explain it to them...
With your unglided wand hooked to your TM, running at working speed, lift the wand up in the air. For arguements sake we will say that your wand is moving 200 cfm through the tube. Now place that wand down on your presprayed carpet. It digs down into the pile and locks onto the carpet. You are now moving about 50 cfm through that wand due to the restriction of the carpet pile. NOW take that same wand and put a hole glide on it. Lift it in the air like before. You are now moving only 150 cfm's due to the restriction caused by the holes. Now place that glided wand on your presprayed carpet and because of the radius, and the bridges of Teflon it cannot lock down on the carpet. You are now moving 100 cfm through the carpet fibers while working, with no decrease in the lift your truck creates. You are moving MORE cfm while working. That is how a restrictive device like a hole glide will actually move more cfm and dry the carpets much better.
There are a few other principles that play into the formula as well: When you narrow an apperture the air moving through it accelerates ( Bernoulli's principle), and air moving through a hole tends to react like air in a tornado, further accelerating the airflow and greatly increasing the lift at the carpet.
If you have ever used a water claw you understand the advantages of using holes over slots when it comes to water extraction. There is also a reason Chem Dry went to tiny holes on the skids of their RX20's; IT DRIES THE CARPET BETTER, FASTER, AND MORE EFFICIENTLY THAN A STEEL SLOT, or even a Teflon slot for that matter.
Now as to the holes vs. slots question: Here is my analogy:
I tell people that the hole glide is the Ferrari: High performance (easiest push and fastest dry) but it requires a lot of maintenance to perform at it's peak (thorough prevaccing or cuffing the "chunks"). The slot glide is the Honda. It performs good and requires little maintenance ( prevaccing not usually required), but it is no Ferrari. It will still blow a horse and buggy (steel lipped wand) out of the water.
Who is your local supplier? If they carry glides have them give you a hands on demo so you can see/try for yourself. It is also really interesting to try a hole glide and a slot glide side by side with an unglided wand. Slots raise the velocity of the air moving through the slot due to the narrowing of the apperture, the round radius of a slot glide also helps prevent it from locking down onto the carpet. But the slot shape of the apperture is not as efficient as a hole at moving water (think tornado). That is why they perform better than a steel lipped wand, but not as good as a hole glide. They do provide more agitation than a hole glide does though. But you really are not supposed to be using your wand to agitate, the wand is a rinsing tool. Those who won't give up their "scrub wand" usually prefer slots over holes.
One more note: An ill-fitting glide will perform WORSE than no glide at all, a good fit is ESENTIAL. If anyone has a glide and is NOT experiencing better dry time, there is an issue...either it does not fit well due to variations in the wand, wear or bending of the wand lips, it is the wrong glide for that wand, or any other posible problem. Most of these issues are fixable. I recommend you call the manufacturer of the glide to get help diagnosing the problem, or ask the supplier you purchased it from for help resolving the issue.