How do I seal a garden hose against a nipple?
Just last month I was attaching new hose ends to repair some hoses at my daughter's house. I was using hose ends like these equipped with barbed ends and die cast clamps as shown:

          

I found that the hoses being repaired had molded in ridges inside the hose that interfered with the sealing of the barbed fittings. The drawing below shows what a cross section view of the end of the two types of hoses had inside:



I found it necessary to use a narrow very sharp blade to trim away the extra material on the inside of the hose. Without doing that the hose ends would leak no matter how hard I screwed down the clamps around the hose. 

It makes me wonder if the hose manufacturers are putting those ridges inside the hose to discourage DIY repair and force more new hoses to be purchased.