If Dagwood Bumstead had seen them, his projects would have been fine.
Here is what they are and how they help.
Step 1: Two Size Groups ; Two Types of Joints ; Buy 2 or More Clamps
There are two sizes of corner clamps.
The smaller three inch size is usually used for picture frames
The larger size is used for making shelevs and the like.
If used carefully, either can be used for most projects
The corner clamps can be used to make a corner, such the top of a book case to the side of a bookcase
And they can be used to make a "T" joint, the end of one piece to another
Buy In Pairs
Its usually better to use these in pairs because one usually is binding both ends of a board.