sleeping in hostels

All of these things depend on the hostel you are staying at. Some hostels will not allow you to use your own sleeping bag (possibility of bringing bed bugs with you), although some allow sleepsheets. I don't carry either with me and I have never needed either. Most hostels will provide linens for free, although some charge €1-2 to rent them. You will want to bring a small travel towel though, as most hostels do not provide towels. (Some rent them for a few euros.)

I do have a sleep sack, but I just bought a $5 full size sheet at Target, folded it in half, and sewed the bottom and side up.

Several hostels I've stayed at have lockers you can use for a small fee, others have a luggage room where they just throw everybody's luggage in a pile. This is something you should ask each individual hostel about as it varies.

I have no idea about Egypt.

Jennifer gave you pretty good advice already. I have never needed a sleep sack. A towel is very handy to have though - I purchased Rick's microfiber towel. Some places had lockers, and others didn't. But, it depends on the hostels you book on what you will need. Look on hostelbookers.com, hostels.com or similar websites to find out specifics for each hostel and to look at others' reviews.

To see if a hostel provides blankets and lockers you will need to check with that particular hostel. I think majority of them do provide all that stuff for free. Some hostels charge a fee for the big lockers that are usually in a large common room, but the ones that are in the dorms should be free. Make sure you check this with your hostels, because it's important. I always put my stuff in the locker. You also will need to provide your own lock. Get a heavy duty one.They are harder to cut off.
You can check out hostels.com or hostelworld.com

I have yet to stay in a hostel that didn't provide bedding (although I hear they still exist). On our last big trip we each made a sleep sack out of older sheets and added them to our carry on. We used them exactly once. Even then the place had free bedding, but we felt we needed to justify packing them.

I doubt I'll ever take a sleep sack again. If I did, it would be a silk one. Primarily because they weigh less and pack smaller.

Every hostel I've stayed in had a locker next to your bed. The lockers were pretty standard and always seemed sturdy. Bring your own lock. I usually bring two locks. One is a backpack lock that looks like a caribiner(?) with a combo on one side. The other is a small master lock with a wire that I use to connect my bag to the overhead luggage rack on trains. No one has ever tried to grab my bag on a train but it's there just in case.

The big thing is don't leave stuff laying around or out of your site. Hostels are safe but petty theft happens.

Thank you for your responses. I have emailed a couple of hostels with some of my questions but have not received replies. Not sure if that's a sign of a disorganized hostel. Glad to have your input.