A classic that still performs
The other reviews are correct - this is an old standby that still finds many uses in the shop. Mine happens to be a woodworking shop, so I use this block mainly to hand sand in areas where my power sanders cannot reach and also to lightly sand between clear finish coats. I have used this block with great results on many projects.

Now, having said that, changing paper on this sander is not as efficient as it could be. While you flex the lip on each end with one hand, you must slide the paper in with the other while keeping the paper straight and not puncturing your fingertips on the little nails that grip the paper... I have done it hundreds if not thousands of times successfully, but I gripe about it every time. For under 20 bucks there are other sanding blocks out there that supposedly solve this problem but I haven't tried them yet (such as the Preppin' Weapon).

This is a classic, but not perfect, product that still performs well.

A MUST HAVE TOOL
What can I say about a sanding block that might be helpful? This age old design works well, and this model is nearly indestructable. The high quality rubber will last a lifetime,Comfortable to hold and use.The only problem I've had with it is the spikes that hold the paper, tend to rust. No big deal really I just cleaned em up and put a dash of (dri-cote) see (BOSTIK) and that was the end of that.The design is old but it's good so, dont be afraid it's money well spent. Now get out there and sand something smooth.

The sander your father used
This sanding block doesn't have all the new bells and whistles. but it is still the best for hand sanding a flat or evenly curved surface. It is easy to hold and put pressure on when sanding. It allows you to use regular sheet sanding paper ripped into fourths (easily done on a sharp edge, just like ripping a regular sheet of paper), so you don't have to waste money on expensive specialty sanding papers that only fit one type of sander. The only downside with the block is that it takes some effort to load replacement sandpaper, but that doesn't have to be done all that frequently, as you can load about four sheets at a time and just rip off the used sheets as they are used up.