Pretty good, but do this....
The carpet repair kit (purchased at Amazon.com) works well.  However, here are a couple of suggestions that will make it easier for you.<br /><br />1.  If you're patching a carpet that's glued down to a concrete floor, take it easy when cutting out the bad part with this tool.  Getting too aggressive will break the blades and the center point.  I did that.<br /><br />2.  If you do break the blades there are two spares in the kit.  If you break the point just file or grind a new point on it.  It's adjustable in height so this fix will work OK.<br /><br />3.  The instructions and product description seem to say that the glue circles are sticky on both sides.  They're not.  This is apparently because the adhesive originally used would not stick all that well to the carpet.  Instead, the circle now is sticky on just one side.  This should be used to stick the circle to the sub floor, concrete, or whatever.  After the circle is stuck to the floor spread some of the seam sealer adhesive on the top of it (brown paper side) and then place the patch.  The sealer will stick the carpet patch to the brown paper.<br /><br />4.  The instructions say to wet the sticky side of the circle after peeling off the protective white sheet then work the circle under the edge of the carpet that is left after cutting out the damaged piece.  This is pretty nearly impossible, at least on a glued down carpet.  What I did, instead, was cut the circle into quarters yielding four pie shapes (before peeling off the white protective paper.  This allows you to work each piece under the edge of the carpet placing the pointed end at the center of the cut out circle.  Then do the same for each of the remaining sectors, aligning them against the previous one with their points together (re-assemble the pie).  Wetting the adhesive is quite important because it is pretty aggressive stuff and you'll have a heck of a time placing it if you don't wet it first.<br /><br />5.  One more thing.  If you're working with a glued down carpet be sure to work a putty knife, etc. under the edge of the carpet that remains after cutting out the damaged area, to allow enough space to slide the sticky circle under the edge.  Then, after the adhesive circle is in place and before placing the carpet patch in the hole, spread a little of the seam sealer between the top of the adhesive circle and the bottom of the remaining carpet to glue it back down.  Then spread a small bead of sealer along the edge of the remaining carpet and spread some on the brown paper side of the adhesive circle that you stuck down as pieces of pie.  Then you can insert the patch and finish as in the instructions.<br /><br />It makes a pretty nearly invisible patch.
Rating: 4 stars