Here are the instructions for how to sew a top sheet for a toddler bed.
First, cut a square of fabric 45 inches by 60 inches.
Then, cut out a six inch square from each of the bottom corners.
Then, take the edges of one of the bottom squares, and sew them together, right sides together. Repeat with the other one.
Make a casing around the two long sides and the bottom edge of the fabric. To make a casing: Turn under (wrong sides together) 1/4 inch all the way around and sew around it. Then, turn under again 1/2 to 3/4 inches around. Sew again as close to the previous stitching as possible. Leave a hole about half way down on each of the long sides.
Then, put about 85 inches of elastic through the bottom half of the sheet using the holes you left in the casing. Start by using a medium to large safety pin and pinning one end of elastic to the sheet right next to the first hole in the casing. I use another pin to pin through the other end of the elastic to make it easier to pull the elastic through the casing. Then, I gather the casing over the safety pin and pull the elastic all the way through the casing until I get to the hole on the other side of the sheet.
Then, I keep pulling it and moving the gathers of the casings along the elastic until the bottom looks about as gathered as the bottom of a fitted sheet.
Then, I sew a straight line across the casing right before the hole I left to sew the elastic in place. I do that on both ends of the elastic.
Then, I sew the holes closed.
The final step is to hem the top. You can either do just a turn twice and hem or do a wide hem like you would for a normal sheet. To do a wide hem, turn under the first time 1/4 inch and sew and then turn under again about 2 1/2 inches and sew as close to the first stitching as possible.
If you choose to make these sheets and have any questions, feel free to email me. firstname.lastname@example.org