In the off-season I want to tan some of my beaver, coyotes and muskrats and attempt to make a hat, mittens and a few other things. I see people talking about blocking fur first? What does this mean and how do you do it? Thanks.

After a pelt is tanned,it will be all stretchy,baggy and out of shape and will also likely need some minor repairs.
Before using a pelt in a garment,all defects are repaired(cut out and sewn).Then the leather is soaked with warm water,folded leather to leather and rolled up and allowed to sweat into the leather.
Then after an hour or so,the pelt is stretched and pinned or stapled to take all the pucker and most of the stretch out of the leather,and allowed to dry for 24 hrs.
Now it will be ready for marking the pattern,cutting and sewing. Some garments are blocked and stretched out many times during construction.For example,the initial blocking after repair,then if skins are let out,they are blocked again after letting out.Then also after the main let out pieces are sewn together into collars, sleeves,front and back of a coat for example,these are also then blocked again to shape before final construction.
Pelts can be blocked to any shape,for example beaver can be blocked oval,or square depending on use or pattern applied.

Thanks Boco for all the detail and explanation. The hat that you posted a picture of with the pattern drawn out a while back is one of the things I want to try. Guessing it won’t turn out looking like that one but I’m excited to try. So nice that you share so much of your knowledge with us newer trappers!

Happy to do so,Madbeaver.One thing to do when blocking.Pin\staple the head area first,then pull the bottom snug,then the sides.Try to keep it uniform,and before laying on your pattern,mark a centerline.Also take note of any weak spots in the fur like armpits and belly and work around them.You don't want the thin fur in your pattern pieces.(not an issue with beaver).After you remove the pins/staples from the dry blocked pelt you can mark the thin fur areas with pins from the fur side and then mark them on the flesh side of the blocked pelt with a pen before you lay out your pattern.

Boco, your knowledge of fur and trapping is good. Thanks for sharing...pictures even. Nice looking 'put-up.' Such good info from so many people on this forum.