There are usually only 4-5 sentences in a Stretch It.  It is different from a Finish It because you are not telling an entire story. 

They found a pumpkin.

Who is they?

Jim and Maggie found a pumpkin.

What kind of pumpkin?

Jim and Maggie found a large pumpkin.

Where did they find the pumpkin?

Jim and Maggie found a large pumpkin in the field.

Why did they find the pumpkin?

Jim and Maggie found a large pumpkin in the field while they were looking for the perfect pumpkin.

This is how a finished one would look:

Stretch It

They found a pumpkin. 

Jim and Maggie found a pumpkin.

Jim and Maggie found a large pumpkin.

Jim and Maggie found a large pumpkin in the field.

Jim and Maggie found a large pumpkin in the field while they were looking for the perfect pumpkin.