In general it is true that you want pretty firm and secure lines under the boat to stop your cover pooling – it is especially true for flat covers. For a decade we just had plain lines that we used to tie, and to be honest they worked OK but were a bit fiddly to tie really tight. At our club, two types of clip are common.
This is the first and very common type. The strap is a preset length, and the two plastic ends clip quickly together. I think this is great and very convenient. I’m not sure that they stay 100% tight though. Maybe they slip when left alone, or maybe as one does them up they give a little – so you do see some in the boat park a bit too slack. That’s when the trouble starts….
We have this second type. It takes a few seconds longer to do up, but at least you do know that you leave it firm and tight every time you leave the boat. Once you have threaded the loose end of the strap through the buckle, you just give it a tug and it self locks very effectively. So look for these especially on a flat cover…..