Bees are essential to food production. Approximately one out of every three mouthfuls of food comes either directly or indirectly from plants that were pollenated by bees. Without bees the world goes hungry.
The species most important and most at risk are the solitary Mason Bees and Bumble Bees.
Why not do your bit to help bumble, mason and carpenter bees survive by providing them with somewhere save to sleep. A bee hotel is perfect for them and the benefit to you is a healthier, better pollenated garden.
Building such a house (or bee hotel if you prefer) is the easiest DIY project you can imagine.
To make a bee house you will need

Drill holes in your block of wood as shown below

Cut a piece of bark to size and nail it on as a roof and your beehouse is complete.

Plase on a south facing wall or fence anywhere between 1 and 2 metres of the ground. If you make a few houses and place them near apple treese you can almost guarantee a bumper crop.
If you have a larger block of wood to spare why not upgrade to a bee hotel. Someone might get a buzz out of that!
