Here is a re-post of a comment I made on a related subject of Glides. Hope this helps give anothers perspective and experience:
"I would like to interject my experience and findings. Technically, the normal wand opening at the nozzle is designed to focus ALL the available velocity and air-flow at the carpet surface. And, the majority of the time, the wand will not be in a situation where a "lock-down" is achieved because of the very nature of the fibers creating an uneven surface (s).
In regards to Glides and the advantage of this product, (They are nothing new to the hard floor industry) it will not "increase" operating velocity/air-flow of ones machine ; rather perhaps to concentrate it, particularly with regards to the hole glide style. HOWEVER, if the goal is to concentrate it in a specific area, by doing so, we also are reducing the VOLUME which directly correlates with the achievement of the very word and process of: Extraction. And, the element of extraction is what relates to a cleaner; dryer carpet.
The other aspect/element the Operator loses using them is foregoing any vital "mechanical action" (scrubbing)in regards to breaking down surface tension. Remember the descriptive term: "Scrub-Wand"?
IMHO, I have concluded that Glides (ex: Nozzle shoes not restricting the vacuum intake) major benefit are to make the wand push easier over the carpet, and this alone can be a major benefit to some. Furthermore, I do know that for those who love them, there are those who have taken them off for reasons listed.
But, I have also found that if anyone wants to achieve all the vital elements that a wand should provide which I have listed above, and who want to keep their air-flow moving in "Lock-down" situations, the way one does this is to drill 2- holes on the front lower sides of their wand nozzle. This will alleviate lockdown and draw the air up the inner sides and wipe it right up the barrel; something we did about 10-15 years ago to many of our 1-jet wands which I am sure are still in use.
Alleviating lock-down is not a new thing because this was something that the wet-dry Industry solved way back in the 50's when they drilled 2- openings on the outer sides( or ends in this case) of the wet-dry pick up wands. By doing this it made it alot easier to push/pull the nozzles over a hard floor yet accomplish the required Extraction and drying process."
The very best to all;
Ed Valentine