Most Knee kickers are pretty much the same apart from price
The metal ones that are sold in this country are mainly made by roberts and imported from the US. Other makes are orcon,gundlach and crain, all US companys.
The ones sold by B+Q are approx 1/2 size and are toys, I would have no use for them. They are made by stikatak based in ruislip , west london and are aimed at the DIY market
I personnally use none of the above but prefer to use kickers that have 'sharks teeth' instead of the normall adjustable pin type such as the above. As meantioned above these cost about £30.00 from argos compared to about £90.00 for the normall types. I have both, the cheap ones are FAR supperior to the expensive ones in my view and I have been fitting for over 30 years(cleaning is a sideline)
If you are going to use a knee kicker then the key thing is to get the depth adjustment right. Too deep and you will puncture the backing maybe leading to filtration soiling problems later on, particularly on pale carpets. As carpet cleaners I am sure you have all seen this, not deep enough and you will be relieing on the nap inserts to grip the face fiber, this a recipe for desaster.
As far as an easy safe way to stretch carpets is concerned the answer is to use a power stretcher.
I usually carry two Roberts GT powerlok power stretchers with me at all times, though I don t think carpet cleaners need to go to these lenghs.
If as carpet cleaners you feel the need for a power stretcher then last time I looked HSS hired them out at about £25.00 per day. Judging by the photo in the catalouge they use the Crain ones.
You do need to know what you are doing with these.
Michel